Drilling Innovations That Will Forever Change the Oil Industry

Oil drilling has now been practiced for over a century. The sector has developed by leaps and bounds as a result of several technological breakthroughs. This expansion has resulted in new advances in oil production that are altering the face of our civilization.

As early as 1880, the globe witnessed one of the earliest developments known as the rotary drill, which dramatically enhanced the oil drilling process. This rotary drill, however, was just the beginning of a lengthy line of subsequent developments that would eventually replace it in the twentieth century. In this post, we'll look at some of the most significant breakthroughs in oil production efficiency.

1. Offshore Drilling and ROVs

Oil drillers quickly discovered that wells located near seashores generated the most oil. This is why the industry needed to develop technologies for extracting oil from the seafloor. Drilling companies built oil rigs on several wharves in the 1980s, but the first oil well on land was discovered somewhere about 1947.

Remotely operated vehicles were among the early technologies that aided the establishment of these offshore drilling enterprises (ROVs). The US military was already using this technique to recover equipment that had been lost at sea. The oil sector was exploiting ROVs for their own purposes by the 1970s.

2. Hydraulic Fracturing

Fracking, or hydraulic fracturing, is another new technology that Shale Gas relies on. This approach, which was created in 1940, has grown in popularity. Fracking is based on tight reservoirs, which often contain oil-bearing rocks with small holes, implying that the flow of oil from these is limited.

Drillers utilize fracturing to stimulate these wells by putting chemicals mixed with water into the well to produce pressure. This pressure, in turn, causes fractures in the rocks that can be hundreds of feet long. After these fissures are created, oil is allowed to flow freely out of the rock. According to numerous studies, fracking has contributed to an additional seven billion dollars oil barrels from wells in the United States.

3. Seismic Imaging

Initially, looking for oil wells was based solely on where oil had bubbled to the surface. Because most oil wells are buried far beneath the earth's surface, they cannot be discovered. Digging deep wells to set up rigs only to find barren patches was also highly costly.

Geologists were brought in to devise methods for locating oil wells that were hidden. They devised numerous approaches, the most important of which was 3-D seismic imaging. This system transmits sound waves into the ground and detects signals as the waves bounce off of obstacles.

This technology not only assisted in locating the most productive locations for establishing oil production units, but it also reduced the number of holes that were drilled without success.

4.   Measurement-While-Drilling Systems

One major disadvantage of seismic technologies was that they did not provide drilling operators with precise information about the amount of oil they were working with. These concerns were resolved in the 1980s thanks to a technology known as measurement-while-drilling (MWD).

With this system and its reliance on'mud pulse telemetry,' operators were able to collect and analyse real-time data, allowing them to establish the state of the oil well. This technology, in turn, enabled operators to drive oil wells in different ways based on the data they had gathered.

5.   Horizontal Drilling

We emphasized the potential of operators to steer their oil drilling operation in multiple directions while discussing MWD technologies. This capacity to drill in directions other than straight has become one of the most significant technological achievements in the history of the oil drilling process.

Oil reservoirs tend to be spread out horizontally from time to time, making vertical wells an ineffective method of extraction. This is why these technologies enable operators to dig vertically initially and then pivot to a horizontal well at the 'kick-off point.'

This technology has not only enabled the extraction of oil from horizontal wells, but it has also assisted operators in conducting their operations in a more environmentally friendly manner. The first horizontal wells were dug in 1929, but the process was prohibitively expensive at the time. However, with the introduction of hydraulic fracturing, horizontal drilling became a more inexpensive and realistic choice. By the late 1980s, nearly all oil drilling companies across the world were adopting horizontal drilling.

Read More → Drilling Innovations That Will Forever Change the Oil Industry

Multilateral Drilling

Multilateal Drilling

Sometimes oil and natural gas reserves are located in separate layers underground and multilateral drilling allows producers to branch out from the main well to tap reserves at different depths.

This increases production from a single well and reduces the number of wells drilled on the surface.

A multilateral well is a single well with one or more wellbore branches radiating from the main borehole.

It may be an exploration well, an infill development well or a reentry into an existing well.

It may be as simple as a vertical wellbore with one sidetrack or as complex as a horizontal, extended-reach well with multiple lateral and sublateral branches.

General multi- lateral configurations include:

• Multibranched wells, forked wells, wells with several laterals branching from one horizontal main wellbore, wells with several laterals branching from one vertical main wellbore, wells with stacked laterals, and wells with dual-opposing laterals.

These wells generally represent two basic types:

vertically staggered laterals and horizontally spread laterals in fan, spine-and-rib or dual-opposing T shapes.

A successful multilateral well that replaces several vertical wellbores can reduce overall drilling and completion costs, increase production and provide more efficient drainage of a reservoir. Furthermore, multilaterals can make reservoir management more efficient and help increase recoverable reserves.

Regardless of the level of complexity, multi- lateral wells today are drilled with state-of-the art directional drilling technology, but there is always a certain risks ranging from borehole instability, stuck pipe and problems with overpressured zones to casing, cementing and branching problems.

Advantages of multilateral systems increasingly outweigh the disadvantages.

Multilateral wells configuration enhance productivity.

In shallow or depleted reservoirs, branched horizontal wellbores are often most efficient, whereas in layered reservoirs, vertically stacked drainholes are usually best.

In fractured reservoirs, dual-opposing laterals may provide maximum reservoir exposure, particularly when fracture orientation is known (From Schlumberger Oilfield review)

Read More → Multilateral Drilling

Horizontal Drilling

Horizontal Drilling

Horizontal drilling is a directional drilling process aimed to target oil or gas reservoir intersecting it at the “entry point” with a near-horizontal inclination, and remaining within the reservoir until the desired bottom hole location is reached.

While the construction of a directional well often costs much more than a conventional well, initial production is greater of a conventional well.

Horizontal drilling provides more contact to a reservoir formation than a vertical well and allows more hydrocarbons to be produced from a given wellbore.

For example, six to eight horizontal wells drilled from one location, or well pad, can access the same reservoir volume as 16 vertical wells.

Using multi-well pads can significantly reduce the overall number of well pads, access roads, pipeline routes and production facilities, minimizing habitat disturbance, impacts to the public and the overall environmental footprint.

Horizontal wells are usually drilled to enhance oil production and in some situations the improvement may be dramatic – enabling development of a reservoir which would otherwise have been considered uneconomic.

There are many kinds of reservoir where the potential benefits of horizontal drilling are evident:

• in conventional reservoirs
  • Thin reservoirs; Reservoirs with natural vertical fractures;  Reservoirs where water (and gas) coning will develop; thin layered reservoirs; heterogeneous reservoirs;
• in unconventional reservoirs
  • shale gas/oil, tight gas/oil, CBM, heavy oil, oil sands, etc

The initial vertical portion of a horizontal well is typically drilled using the same rotary drilling technique that is used to drill most vertical wells, wherein the entire drill string is rotated at the surface (the drilling of vertical sections is also possible by the use of downhole motor just above the bit, like the VertiTrak or TruTrak, where only the bit rotate while the drilling string remains firm).

From the kickoff point to the entry point the curved section of a horizontal well is drilled using a hydraulic motor mounted directly above the bit and powered by the drilling fluid.

Steering of the hole is accomplished through the employment of a slightly bent or “steerable” downhole motor (today the technology of directional drilling has improved by the use of the “RSS: Rotary Steerable System” that permit to steer an hole continuing the rotation of the drilling string. The RSS increase the safety and the drilling efficiency).

Downhole instrument packages that transmit various sensor readings to operators at the surface are included in the drill string near the bit.

Sensors provide the azimuth (direction versus north) and inclination (angle relative to vertical) of the drilling assembly and the position (x, y, and z coordinates) of the drill bit at all times.

Additional downhole sensors can be, and often are, included in the drill string, providing information on the downhole environment (bottom hole temperature and pressure, weight on the bit, bit rotation speed, and rotational torque).

They may also provide any of several measures of physical characteristics of the surrounding rock such as natural radioactivity and electrical resistance, similar to those obtained by conventional wire line well logging methods, but in this case obtained in real time while drilling ahead.

The information is transmitted to the surface via small fluctuations in the pressure of the drilling fluid inside the drill pipe.

Read More → Horizontal Drilling

Drilling with Coiled Tubing for Multilateral Wells

The petroleum industry is constantly driving to reduce capex and increase economic recoverability while minimizing environmental impact and surface footprint. By combining the three advanced drilling techniques of multilateral drilling, underbalanced drilling (UBD) and directional coiled tubing drilling (CTD), an operator can capture significant value out of known reserves.

The highest well productivity is achieved through maximizing reservoir contact per well/surface slot and minimizing reservoir damage. Multilateral drilling reduces capex through drilling multiple reservoir sections per surface slot while also increasing reservoir contact per surface slot. UBD minimizes reservoir damage, which maximizes the productivity of each lateral. CTD is inherently set up for underbalanced operations (UBCTD), and CTD bottomhole assemblies (BHAs) can achieve high build rates of up to 50 degrees per 30 m (100 ft) to allow multiple targets to be accessed from the mother wellbore.

Selecting a BHA

A directional CTD BHA consists of a coil connector, cablehead, electric or mechanical disconnect, downhole orienter, sensor package, motor or turbine with a bent housing, and a drillbit. Drilling directionally on coiled tubing (CT) is similar to conventional slide-and-rotate drilling on a rotary. As CT cannot be rotated from surface, all the rotation needs to be carried out downhole through the orienter. The rotating orienter allows the toolface to be set from surface or for the motor to be rotated to drill a straight hole.

Service companies also can provide additional BHA modules such as a gyro module for orienting a whipstock and for drilling in the presence of magnetic interference immediately after exiting the casing.

CT drilling faces two fundamental challenges: transferring weight to the bit and length limitations of the lateral sections. If the well trajectory plans for high doglegs, then it can be difficult to transfer weight to the bit. This is accentuated by the inability to rotate the whole drillstring as in conventional drilling. It is essential to have a weight-on-bit (WOB) sensor in the BHA so the driller can see that the weight is actually being transferred to the bit and react accordingly. The length of laterals that can be drilled with CT also are affected by the tortuosity, but this is particularly true in horizontal sections. The more tortuous the wellbore, the shorter the lateral length will be. CTD BHAs that have a continuous rotating orienter prevent this tortuosity from occurring and therefore maximize the available WOB and lateral length (Figure 1).

FIGURE 1. A straight wellbore increases the potential length of a lateral section compared to a wavy wellbore. (Source: AnTech)

Designing a multilateral well

All well designs require a multidisciplinary team to be successful. When designing a multilateral well, an integrated team of subsurface specialists and directional drilling specialists is even more essential to successfully drill the well. The well design and completion strategy is heavily affected by the reservoir characteristics, horizontal and vertical permeability, the geological structure, and geosteering requirements. The first step is to clarify if significant productivity gains can be made from utilizing multilaterals over other techniques. Once established, it is an iterative process between the directional drilling contractor and the operator’s engineering and subsurface teams to find the best way to design the well.

There are a near-infinite number of wellbore paths for multilateral wells. The two most common are stacked laterals and forked laterals (Figure 2). Stacked laterals can access different layers of a laminated reservoir. Forked laterals are all at a similar depth and are most commonly used to increase reservoir contact in a specific formation. Clarifying the objective for the multilaterals early on helps reduce the number of iterations required of the trajectory.

FIGURE 2. Stacked laterals offer access to different layers of a laminated reservoir, while forked laterals are at a similar depth and help increase reservoir contact in a specific formation. (Source: AnTech)

Once the trajectories are drafted, the wells must be modeled to ensure drillability and to specify surface equipment. For the CTD section the main areas for analysis are the available WOB, CT lock-up limit, borehole cleaning and surface pressures. The CT can be specified from these models. Production and geomechanics models also must be run to ensure the separation equipment is suitably specified and the amount of the underbalance applied to the wellbore does not cause wellbore stability issues.

Sidetracking techniques

To create the additional well path from the mother wellbore, a sidetrack must be initiated. There are two main categories of sidetracking a well: cased-hole sidetracks and openhole sidetracks. The cheapest and fastest way to carry out a cased-hole sidetrack is to use a whipstock and a window milled in the casing rather than section milling.

Multiple whipstocks can be set in the mother wellbore and retrieved if required. For openhole sidetracks the drilling BHA is used to create a trough in an inclined section of the wellbore. Once the trough is initiated, the WOB can be increased to carry on the borehole section. An openhole sidetrack also can be initiated off a cement plug with special procedures.

Since CTD BHAs operate on wireline, this allows significant amounts of real-time data to be received from the BHA. This helps to speed up the sidetracking process because rather than relying completely on time drilling, the directional driller can see the WOB and torque-on-bit responses to each operation and optimize on the fly. This is the case with both openhole and cased-hole sidetracks. A special module is required to monitor the casing milling operations since the vibration levels are so high.

Geosteering

A multilateral will not provide a good return on investment if the laterals are not drilled into the target zones. The options for geosteering on UBCTD are relatively limited compared to a conventional LWD service. Gamma ray and resistivity are available on certain CTD BHAs. A biostratigraphy service also can be used to identify changing formations. The UBD package can provide a significant amount of data that can be used for geosteering and reservoir characterization while drilling. The large amount of additional information that can be gathered from the real-time downhole sensors and the UBD package, if used correctly as part of an integrated data acquisition and reservoir evaluation strategy, can remove the need for expensive LWD tools or wireline logs.

Drilling practices

Drilling on CT has been avoided in the past due to concerns over stuck pipe and borehole cleaning issues. When drilling reentry wells using CTD, the borehole size is usually closer to the BHA size than in conventional drilling. In addition, since the pipe is not rotated, a greater focus needs to be placed on good borehole cleaning practices. Every CTD project must be modeled and analyzed to ensure the well can be drilled successfully. When drilling the borehole sections, the real-time drilling parameters must be monitored to identify any indications of borehole problems. Drilling practices also are adapted to ensure the borehole is clean and free of ledges. For example, a short trip must be made at every 46 m (150 ft) to ream the borehole, and at every 91 m to 137 m (300 ft to 450 ft) a long trip back to the casing window must be made. Because the driller is able to see these changes in downhole conditions at surface, there is an opportunity to prevent these issues and optimize the uptime of the operation.

Read More → Drilling with Coiled Tubing for Multilateral Wells

Optimize Wells with Rotary Steerable Systems

In any well delivery operation there are three drivers—drilling efficiency, accurate well placement and high-quality wellbores.

The main objective in directional drilling is to accurately position the well within the target to optimize returns. Nevertheless, wellbore quality is just as important a factor that must be considered—a precisely placed well does not necessarily mean the wellbore itself is ideal for later completions. While placing high-integrity wells in the best locations, drillers must also strive for higher performance during operations, which entails getting to total depth faster with less flat time.

High-quality wells delivered ahead of plan can help operators see a positive impact not only on cost per foot, but also cost per barrel produced. Early production, efficient post-drilling operations and optimum field development plans are all affected by superior well construction.

Extended-reach drilling (ERD) services provide a solution to restricted reservoir production, enabling operators to more efficiently develop their assets by maximizing the exposure of the targeted intervals and eliminating the need for additional platforms.

For example, in the Middle East an operator was planning to drill an ERD well in a challenging high-temperature (HT) geological environment. As an additional challenge, the subsurface target was located beneath an urban area. In-depth prejob planning and risk assessments were conducted to design an integrated drilling system that included the PowerDrive VorteX rotary steerable system (RSS) to deliver high ROP, the PowerDrive Orbit RSS to drill an abrasive HT interval, logging while drilling (LWD) tools, drilling fluids, custom drill bits and hole-cleaning and surface logging services. The well was delivered within the planned time, with no HSE incidents, and fully within the planned subsurface targets. The well also set the record as the first and the deepest pre-Khuff HT well drilled by the operator.

Powered By Experience

Rotary steerable systems have evolved throughout the years to continuously improve upon key deliverables: accurate wellbore positioning, optimum borehole quality and maximum drilling efficiency. A wide offering of systems makes achieving all three possible—in multiple applications.

All of the Schlumberger PowerDrive RSSs share distinctive characteristics to achieve drilling objectives. Rotation and torque are fully transmitted throughout the body of the tool to eliminate dragging components and enable maximum drilling performance to the target depth. These features also allow optimum efficiency when pulling out of hole and deliver maximum well integrity for post-drilling operations.

The systems also measure inclination and azimuth close to the bit. This close proximity and measurement accuracy is critical in maintaining an accurate 3-D well trajectory while pushing for drilling performance to enable precise kickoff delivery. Another inherent feature is the downhole closed automation loops, which provide directional consistency during well construction. In a recent drilling operation in the North Sea, the PowerDrive Orbit RSS reached a target total depth of 950-m (3,116-ft) section in one run and helped avoid close-proximity wells. An average of 25 m/h while drilling the first 475 m (1,558 ft) of the section was also achieved despite stick/slip severity of 90% to100%.

More Power In More Places

While all RSSs seek to eliminate sliding and provide basic inclination measures, there are more factors to consider when choosing a system. With the variety of fully rotating designs, the technology should be selected to maximize performance for each application. This is why versatility is a key advantage. Different steering mechanisms match customer needs in the planning phase. They also meet any unexpected challenge during the execution of the drill plan.

The PowerDrive family comprises RSS for a host of applications, including operations that require extensive runs, high ROP drilling, vertical drilling and high dogleg severity. The latest member of the family, the PowerDrive Xcel RSS, was specifically designed to handle the challenges inherent during extended reach drilling, sidetracking and geostopping. The gyrosteering capability of the system enabled an operator offshore Brazil to sidetrack just 1 m (3 ft) below the casing shoe, achieve the full deviation from the pilot well after 16 m (52 ft), and build inclination from 82 degrees to 85 degrees with a dogleg severity of 5⅓ degrees/30 m (even greater than the planned 3½ degrees/ 30 m) despite magnetic interference caused by the 9⅝-in. casing.

Power For Ultimate Performance

With a quarter of a billion feet drilled around the globe, which is roughly twice the circumference of the Earth, the PowerDrive RSS is the most used RSS family in the world. Using these systems, operators have continually broken footage, measured depth and ROP records in North America, Latin America, the North Sea, Middle East, Asia Pacific and the Far East. The RSS family also holds the record for the top 12 longest wells in the world.

The PowerDrive family encompasses a range of directional drilling solutions, derived from expertise and proven success, applicable to any environment. It widens the operating envelope, placing power in the operator’s hands, increasing ROP and lowering costs, however challenging the conditions.

Schlumberger, drilling, PowerDrive Orbit, rotary steerable system

The PowerDrive Xcel RSS was designed for use in high-profile directional drilling operations. It provides inertial directional control in deviated sections— a feature that can be toggled on and off by a downlink. (Source: Schlumberger)

Read More → Optimize Wells with Rotary Steerable Systems

Digitalization Directional Drilling

Super-specification pad-optimal Swiss Army-style walking rigs may generate headlines when it comes to evolution in land drilling, but directional drilling is fast becoming a more accurate indicator of how the sector is evolving as tight formation development enters full field development.

Companies like Baker Hughes, a GE company, have offered sophisticated geo-steering suites combining bits, motors, downhole evaluation and software control to improve ROP for some time. But quietly, and without fanfare, the largest domestic land drilling contractors and their Canadian peers are integrating digital directional drilling capabilities into rig offerings.

The trend accelerated over the last six months when land contractors began purchasing digital directional drilling providers. Acquisitions include Helmerich & Payne IDC’s $100 million purchase of Motive Drilling Technologies Inc. in May, Patterson-UTI Energy Inc.’s $215 million cash and stock purchase of MS Energy Services and Trinidad Drilling Ltd.’s $40 million cash and stock acquisition in August of RigMinder Inc. and its electronic data recorder and bit guidance systems, which integrate the rig and directional drilling tools.

Other drillers, including Nabors Industries Ltd. and Ensign Energy Services Inc., offer directional drilling services and supporting downhole packages that include proprietary mud motors and MWD tools integrated with software to improve directional drilling performance. Nabors, for example, is commercializing a multiple package software suite that includes its recently developed ROCKit directional steering control system.

Meanwhile, Canada’s Precision Drilling aims to “de-man” the directional drilling process via a proprietary directional guidance system that coordinates workflow between the rig’s driller on location and a remote directional driller who oversees several directional drilling projects simultaneously. Precision is using algorithms to convert 14 process and 20 decision points in directional drilling into seven processes and 10 decisions, reducing support crew, time and cost. The system will be fully deployed across Precision’s fleet in 2018.

What’s going on? At the simplest level, it is an opportunity for drilling contractors to capture more revenue per rig in a flat pricing environment. Beyond that, larger drillers are bringing in-house a service that is integral to today’s best practices where precise lateral landing in extended wellbores is as important for boosting hydrocarbon recovery as greater proppant loading.

Digitally enhanced directional drilling integrates software suites, sensors and downhole tools to reduce wellbore tortuosity and generate higher ROP. Digital directional drillers  point to field-tested savings in time and direct costs that are measured in tens of thousands of dollars per well.

Digitalization of directional drilling is disruptive technology. The question is whether it will supplant both personnel and the community of independent service providers.

One other factor promoting the spread of digital directional drilling is that the software is often independent of the rig, allowing smaller contractors to integrate the service into their own rig offerings via third-party access.

Like all wellsite technology, digital directional drilling may require an evolutionary step in perception at the well site that also incorporates specialized human input and flexibility as the best solution for sophisticated problem-solving in a dynamic environment.

Source:Shutterstock.com

Read More → Digitalization Directional Drilling

What is Slant Drilling ?

Slant Drilling is a non-vertical hole drilling form commonly used in natural gas and oil production. This form of perforation is generally for the extraction of oil and gas resources that can not be accessed through traditional vertical drilling. Slant drilling is also used as a means of protecting sensitive environmental areas such as wetlands and oceans. This directional drilling also helps reduce the number of wells and equipment needed for natural gas and oil production. In some cases, drilling tilt provides maximum pressure when a malfunction is vertical.

Natural gas and oil deposits are sometimes found in impenetrable areas such as lakes, mountains, glaciers, or residential areas. Instead of disturbing the existing landscape, a well is perforated at a corner of 30-45 degrees to draw the tank from another location. Well vertical production of underground tanks can sometimes be very difficult because of their shape. In these cases, drilling inclination is necessary for the most effective removal of oil and natural gas.

Slant drilling also offers many benefits to the environment by allowing natural gas and oil production to be kept away from delicate ecosystems. This type of drilling is particularly important in the protection of the marine environment near offshore fields. Slant drilling can allow a single offshore drilling system to access more than 20 wells. This production layout reduces the total number of drilling rigs operating in a single body of water and can reduce the risk to the marine environment.

By allowing more well heads in a single offshore location can also help reduce the overall cost of oil and natural gas. The need for fewer drilling rigs has contributed to reducing the costs associated with the production of natural gas and oil in offshore locations. Onshore production costs have been reduced, allowing drilling rigs to be placed in locations that are more easily accessible to vehicles and pipelines. Production costs can be further reduced by allowing crews to bypass dense, rocky terrain with perforation of non-vertical shafts from a location with fewer obstacles.

Slant drilling can also be used to discharge the pressure after a good blow occurs. In this situation, an alternate well is perforated with an angle to the original well from a different location. Angled shaft removes pressure and stops uncontrolled flow of oil or natural gas to the site. This good relief is then used to pump cement into the original well to say it out until repairs can be made. This loss stop method is particularly useful in offshore situations.

Read More → What is Slant Drilling ?

CONVENTIONAL OIL

Definition Oil is a hydrocarbon formed over thousands of years from the decomposition of dead plants and organisms. Intense heat and pressure on this material triggers a reaction, which leads to the creation of oil

Conventional oil is a term used to describe oil that can be produced (extracted from the ground) using traditional drilling methods.  It is liquid at atmospheric temperature and pressure conditions, and therefore flows without additional stimulation.  This is opposed to unconventional oil, which requires advanced production methods due to its geologic formations and/or is heavy and does not flow on its own. 

You may have heard of these terms used to distinguish different types of oil:

​Light vs. Heavy - this refers to the density of oil and its ability to flow.  Lighter oil can be refined with minimal processing due to higher fractions of light hydrocarbons.

Sweet vs. Sour - this refers to the sulphur content of the oil, sulphur must be removed prior to refining.  When oil has sulphur greater than 0.5% it is referred to as "sour."

Because of these variations, oil quality is a spectrum and the distinction between conventional and unconventional is not always black and white. Generally, however, if traditional drilling techniques are used in the oil production it is considered conventional regardless of its physical properties.

Conventional oil is produced using drilling technologies that utilize the natural pressure of an underground reservoir.  Production of a conventional oil well has four main phases[2]:

Exploration: Geological exploration is a series of technologies that are used by geologists and geophysicists to predict the location and extent of underground oil reservoirs.

Drilling: Once a reservoir has been located with sufficient certainty, a drilling rig is used to bore a hole from the surface to the oil reservoir.  Piping is then inserted, allowing the oil to be brought to the surface.  Some of the oil in the reservoir will be produced using the natural pressure of the reservoir.  

Pumping: Gradually the pressure of the well will decrease as oil is produced. At this point a pump will be connected to allow the remaining oil to be extracted.

Abandoning: After all the economically viable oil has been extracted from the well, the well is filled with cement to prevent any hydrocarbons from escaping and a special cap is placed over it to protect the area[3].

Context

Conventional oil tends to be less expensive and complex to extract than unconventional oil due to the routine nature of the production techniques.  This oil is also the most valuable in global markets because it requires the smallest amount of processing prior to refining to create value-added products. Consequently, many of our global conventional oil supplies have already been extracted, limiting the availability of these source for future extraction[2].

Generally, drilling and well abandonment are well-understood and regulated processes but there are always risks with such industrial operations. In drilling, pressure must be regulated carefully to avoid accidents and immediate environmental impacts like land disturbance must be carefully monitored.  After abandonment, well leaks can occur if improper procedures were taken.  

As with all fossil fuel production, there are also concerns with greenhouse gas emissions from their combustion 

Read More → CONVENTIONAL OIL

Steerable Downhole Mud Motor - Directional Drilling

Steerable Downhole Mud Motor (SDMM) commonly referred to as Mud Motor or Drilling Motor acts much as a positive displacement motor which provides additional rpm to the drill bit from the flow of drilling fluid (mud).

This drilling motor is far different from an electrical motor in it's working principle and operation.

(A lot of people get confused initially)

Since its introduction, the positive displacement motor has undergone revolutionary changes and improvements. Downhole drilling motors have proven to be successful in the most rigorous of drilling environments. From the time of its inceptions, the mud motors have gone extensive improvements that has enhanced its performance, operational and economical reliability. 

Today there are numerous players in the industry providing mud motors for different operational requirements. Few to name are National Oil Varco (NOV), Schlumberger, Halliburton, Baker Hughes, Weatherford, Cavo, Bico, Jaguar, APS, etc. Different mud motors provided by different companies vary a little from each other but, there basic operating principle remains the same. 

Mud Motors have extensively wide range of applications and few of them are listed below:

Conventional Directional Drilling

Side-Tracking

Performance Drilling

Short/Medium/Ultra-short Radius Wells

Air/Foam or Under-balanced Drilling 

ERD Wells

HP/HT Wells

Coiled Tubing Drilling

Vertical Drilling

Casing Drilling

Milling

Coring

Slim Hole Drilling

Working Principle

Mud motors converts the flow energy of drilling fluid (mud) in rotational motion that's utilized in rotating drill bits at a much higher rpm. 

It's imperative that flow rate can be used to control the rpm of the drill bit as per operational requirements. Flow rates for muds are provided by the mud pumps.

Bit RPM = {Flow rate (in GPM) x RPG (Revolutions Per Gallon)} + Rotary RPM 

Note: 

RPG is defined as the revolutions made by bit box and in turn bit, when one gallon of mud flows through it & is mentioned by the manufacturer for each type of SDMM.

While sliding rotary rpm will be zero.

Parts of SDMM:

Simple classification of SDMM parts can be categorized as: 

Top Sub Options

Power Section

Drive Shaft Assembly

Adjustable Bent Housing Assembly

Bearing Assembly

Bit Box

Top Sub options

Top Sub: 

Top sub is simply a cross over housing at the top end of the motor. The lower connection uses a thread that connects to the upper box of the stator housing.

Dump Sub:

It contains a Dump Valve Assembly. This allows the mud to fill or drain from the drill string while tripping.

To avoid the ingress of solids from the annulus when the pumps are off, it’s normal to run a float sub as close to the motor as possible.

The motor will function perfectly without a dump valve - It can be laid down and replaced by a sub having the same connections or run with the ports blanked-off. 

Failure of the dump valve assembly can cause sometimes serious troubles.

Motor Catch & Rotor Catch Top Subs:

The rotor catch system is designed to retrieve the motor in case of a housing fracture. It will retrieve the motor from the upper stator box connection down to the drill bit. The motor catch system has the additional feature of an integral catch flange within the top sub. It will retrieve the motor from the top sub down to the drill bit.

Power Section

Positive Displacement Motors (commonly called a PDM) are reverse applications of a Moineau pump or screw pump. 

It mainly consists of Rotor & Stator.  

Rotor is chrome-plated alloy steel of spiral-helix shape. 

Stator is a hollow steel housing, lined with a molded-in-place elastomer rubber compound. 

A spiral-shaped cavity is produced in the stator during manufacturing. The rotor is produced with matching lobe profile and similar helical pitch to the stator, but with one lobe less. The rotor can therefore be matched to and inserted inside the stator. When assembled, the rotor and stator form a continuous seal along their matching contact points. Fluid is pumped into the motor’s progressive cavities. The force of the fluid movement causes the shaft to rotate within the stator. Thus, it is a positive displacement motor. The rotational force is then transmitted through the connecting rod and drive shaft to the bit.

  

Stage is the distance measured parallel to the axis between two corresponding points of the same spiral lobe. This distance is commonly referred to as the lead of the stator. A slight interference fit between rotor OD and stator ID controls motor power. 

Mud motors are divided into slow-speed, medium-speed and high-speed types. This is done by changing the pitch of the motor stages, by the number of "lobes" and resultant cavities of the stator. 

The greater the number of lobes, the higher the motor torque and the lower the output RPM. 

Increasing the flow rate through a given power section directly increases the output speed. To increase the output speed of a power section without changing the flow rate, the cavity size is changed. A high speed power section will require a larger fluid inlet area (cavity) to allow more fluid throughput into the cavity.

The torque generated by the power section is proportional to the differential pressure applied across the power section and is independent of fluid flow. Generally, the more weight applied to the bit, the higher the torque needed to keep the bit turning, so the higher the differential pressure across the Power Section.

The maximum recommended differential pressure is limited by the stator elastomer. If pressure increases beyond the limits of the elastomer, the stator elastomer will deform, breaking the cavity seal so the mud flow leaks past the rotor and rotation stops – this is commonly known as a stalled motor.

Drive Shaft Assembly

The drive shaft assembly converts the eccentric motion of the rotor into concentric rotation for the bearing assembly via a connecting rod attached to the lower end of the rotor. It transmits the torque and rotational speed from the rotor to the drive shaft and bit. Universal joints convert the eccentric motion of the rotor into concentric motion at the drive shaft. 

It also accommodates any angle set on the adjustable bent housing (or fixed bend housing) and carries the thrust load from the rotor caused by the pressure drop across the power section.

Adjustable Bent Housing

ABH connects stator to the bearing assembly and also houses drive shaft assembly. It has a field adjustable angle-setting to produce a wide range of build rates.

Angle setting may be set to zero for vertical drilling or may be set to any other angle setting as desired. Once the angle is set for the mud motor, it can't be changed when it's down hole and has to be pulled out of the hole to change the angle-setting.

Higher rotary rpm could be used at low angle-setting as compared to a high angle-setting.

Drilling at a higher rotary rpm provides a drill bit with more torsional force provided by the entire rotating drill string as compared to the torsional force provided alone by the mud motor.

(That's the reason why ROP in rotary mode > ROP in sliding mode)

Bearing Assembly

The drive shaft assembly is supported within the bearing housing by radial and axial thrust bearings. It transmits the rotation of the drive shaft assembly to the drill bit and the compressive thrust load created by the weight of the collars and drill string to the rotating bit box & supports the radial and bending loads developed while directional drilling.  

It also carries the tensile off-bottom thrust load produced by the pressure drops across the rotor and the drill bit, as well as any load caused during back reaming. The high capacity radial bearings readily withstand side loads caused by drilling with a deflection device or uneven cutting action along the drill bit periphery. The tungsten carbide radial bearings and angular contact bearing section supports the radial loads along the full length of the bearing assembly, creating a very stiff, strong assembly

Types of Bearing Assembly-

Mud Lubricated Bearing Assembly

Oil Sealed Bearing Assembly

Mud Lubricated Bearing Assembly regulate the flow of mud through the bearing assembly. This diverted mud (usually 4 - 10%) is used to cool and lubricate the shaft, radial and thrust bearings. It exits to the annulus directly above the bit sub. The exact percentage of mud diverted is determined by the condition of the bearings and the pressure drop across the bit. Mud lubricated bearing assemblies can be used in the hottest holes with the lowest aniline point drilling fluids, as there are no elastomeric seals.

Oil Sealed Bearing Assembly is an alternative to the mud-lubricated bearing. A sealed bearing would be recommended where corrosive muds are used, where a lot of LCM of various sizes is pumped or where there is a requirement for a very low pressure drop across the bit (Pbit).

Bit Sub

At Bit sub the drill bit is make up with the motor and it's the only moving external part of the motor.

  

Note: 

In addition to above, different manufacturers can have more or less parts.

The operating conditions and parameters for the mud motors may vary for different manufacturers.

Read More → Steerable Downhole Mud Motor - Directional Drilling

Horizontal Well

What is 'Horizontal Well'

A well that is transformed into horizontal in depth, providing access to the oil and gas reserves in a wide range of angles. horizontal wells has grown in popularity during the 1980s, such as natural gas and oil exploration turned away from less productive than vertical wells. This type of well is used to gain access to conventional sources of reserves.

horizontal wells became economically viable in 1980, such as computerized mapping and directional localization and holes made access difficult to reach deposits of oil and natural gas, easier and more convenient. Of the three categories of drilling horizontal rays - short, medium and long - average drilling is more prevalent

horizontal wells tend to be much more productive than vertical wells. This is because they allow a single well to reach more points, without the need for further vertical wells. This makes each far more productive individual, since most tanks are more productive throughout their horizontal axis that their vertical access. horizontal wells also reduce the risk of introducing water or gas intrusions in the case of oil exploration.

While more productive than vertical wells, horizontal wells tend to be more expensive. Although this cost has decreased over the years tends to be a learning curve associated with exploring new types of fields, especially for developers and inexperienced.

horizontal wells usually starting with the drilling of a vertical well. Drilling vertically allows engineers to examine rock fragments at different levels, in order to determine where the reserves are located. horizontal wells are then "kicked off" from the auction primary vertical, and enter the tank to an "entry point" after the drilling of an arched hole.

The extraction of oil and gas from conventional sources, such as shale rock formations, often requires the use of horizontal drilling technologies.

Read More → Horizontal Well

Vertical Well

A well that is not converted into horizontally in depth, allowing access to the oil and gas reserves are located directly below the point of surface access. Historically, natural gas and oil exploration has involved the use of vertical wells because the directional drilling technology was expensive and complicated. Drilling of vertical wells is considered a conventional method.

Vertical shafts differ directional wells, such as horizontal wells, deep because they require the use of directional drilling. This makes them less expensive to develop, although less productive because of their limited range.

While vertical wells may be less complicated to bring in line of directional wells, their limited angles make them less able to reach a wider part of the underground area. Because a vertical shaft can access only the reserves of petroleum and natural gas directly under, making a large manufacturing industry requires the drilling of many vertical wells. They are especially handy in case of reserve thin layers located over a wide area. Since a vertical well can be drilled in a single direction, the exploration company must estimate the most productive portion of the reserve from the beginning; a vertical drilled well can go right through the reserve, drawing only a portion of the available energy.

horizontal wells usually starting with the drilling of a vertical well. Drilling vertically allows engineers to examine rock fragments at different levels, in order to determine where the reserves are located. horizontal wells are then "kicked off" from the primary vertical shaft.

The extraction of oil and gas from unconventional sources such as shale rock, often requires the use of horizontal drilling technologies because the source can be executed in the horizontal direction. If the reserves are located in a residential area, well vertical drilling would require both the displacement of residents or require them to live next to a tower.

Read More → Vertical Well

Directional Drilling

A drilling technique in which a well is bored to multiple angles. Directional drilling refers more often for the non-vertical angle drilling, including horizontally. It is used both to recover oil and natural gas underground, and is useful in situations where the shape of the tank is abnormal. It is also used to adjust pressure created by the gas in mines (degassing).

As a technique, directional drilling allows oil and gas operators to approach a potentially productive zone, without the need of a well to be drilled directly above that area. A central site can serve holes that reach more and more to non-vertical angles positions. This reduces the number of facilities and which must be constructed and maintained. With no need to build new wells may also lead to the exploration of smaller fields that would otherwise be uneconomical.

Early involved directional drilling tip of the tip with a different vertical angle, resulting in a straight line away from the well. The modern drilling techniques allow the use of tips that can bend; allow engineers to adjust the direction of the well is drilled to a certain extent. This can be accomplished through the use of hydraulic jets

Directional drilling is used in the development of mines, in order to reduce the risk of potentially dangerous gas breakages. In-mine drilling techniques allow companies to create holes in advance of my face.

While the basic concepts of directional drilling date back to the 19th century, has become a popular technique such as computer technology has become more common. The toe angle used for bored shaft can be regulated by a computer using GPS signals to pinpoint the location of an oil and gas field. Engineers create the 3D field models to determine the best location for good, and the best approach to the hole to follow.

Read More → Directional Drilling

Drilling Rig

A drilling rig is a machine that creates holes in the earth sub-surface. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person and are called augers. Drilling rigs can sample sub-surface mineral deposits, test rock, soil and groundwater physical properties, and also can be used to install sub-surface fabrications, such as underground utilities, instrumentation, tunnels or wells. Drilling rigs can be mobile equipment mounted on trucks, tracks or trailers, or more permanent land or marine-based structures (such as oil platforms, commonly called 'offshore oil rigs' even if they don't contain a drilling rig). The term "rig" therefore generally refers to the complex of equipment that is used to penetrate the surface of the Earth's crust.

Small to medium-sized drilling rigs are mobile, such as those used in mineral exploration drilling, blast-hole, water wells and environmental investigations. Larger rigs are capable of drilling through thousands of metres of the Earth's crust, using large "mud pumps" to circulate drilling mud (slurry) through the drill bit and up the casing annulus, for cooling and removing the "cuttings" while a well is drilled. Hoists in the rig can lift hundreds of tons of pipe. Other equipment can force acid or sand into reservoirs to facilitate extraction of the oil or natural gas; and in remote locations there can be permanent living accommodation and catering for crews (which may be more than a hundred). Marine rigs may operate thousands of miles distant from the supply base with infrequent crew rotation or cycle.

Read More → Drilling Rig