Advanced Snake Drill Technique Method for Improving of Oil Extraction Percentage

 Advanced Snake Drill Drill Technique: Method for improving improving of oil extraction  percentage B Sreeranga Pradyumna, Ankur Dwivedi, G Sai Akhil Btech Applied Engineering in specialization in Upstream University of Petroleum and energy Studies, Dehradun

 Ab st rac t: Oil and gas is one of the prime drivers of the world’s economy. The resources of Oil and gas are plenty enough enou gh around the world with 70% of the resources turning out to be unconventional. Economically extracting these resources is always a challenge for the engineers. Different types of drilling techniques like horizontal drilling technique, multilateral drilling technique, etc. are proposed and implemented depending on the type of reservoirs. When the crude oil is trapped in different geological features situated moderately near each other, drilling more than one well in the same place or in the nearby places to extract the oil trapped from different reservoir pockets is very uneconomical. The snake well drill is operated from a single drilling platform to reach number of different reservoir pockets using the state of art software that allows the snake well drill to follow certain complex horizontal paths that cut through shale and sand. They use mobile drilling units that can be moved between the well pads. This prevents dismantling and reassembling drilling equipment at each of the pad making the process faster and saving resources. And also it’s snake like structure helps in achieving maximum reservoir drainage. Though being an improvised technique of extracting the distributed oil profitably, it sometimes fails in some areas. The snake well drill can accidentally miss the target location of oil bearing sands and can drill water bearing sand leading to less recovery of oil. Secondly, there a chance of early water and gas breakthrough at the heel of the well would decrease the recovery. In this paper attempt has been made to propose some techniques to improve the of the Snake well drilling technique and reduce the risk of failure.

the times, conventional drilling is applied for favorable extraction of oil but still two-third of total remains left when end of normal production life of an oil field is declared and even sometimes conventional drilling technique are not preferred and other techniques are approached.  Advancements in technology and techniques allowed exploration in new frontier zones, hard to reach places and some to ultra-deep water. The new techniques proposed are approved after risk analysis and production strategies to minimize the uncertainties. One of those technique trending is snake drill technique of which practice is increasing with time as it ensures better production than conventional drilling in most of the oil fields not having normal conditions and a new possibility for extended reach drilling. But the uncertainty and some points of failure still lies and so improvements and methods are being introduced with time. This paper covers a brief review of the present snake drill technique, the need to adopt this technique with the software or the tools which helped it lead to make higher production at possible minimum cost and uncertainty. It too provides an overview of the champion ch ampion west oilfield and the role of this technique to make it a success. Being a new trending technique some alternate method or solutions are proposed to the flaws of this technique at present time. Type of Drilling Techniqu es :

Vertical Drilling: It is the conventional technique of drilling a well to drill hydrocarbons vertically below the access point. It is the first and foremost method proposed and used for drilling Oil wells. These wells are less expensive as they do not require any directional tools and also give less productivity due to its less range. Hydraulic fracking method is used to improve the production of these wells.

Keywords: snake well drilling; shale; crude oil; well pads; reservoir drainage

Introduction:

Exploration and production of hydrocarbons is a high risk venture. Geological concepts are uncertain with respect to structure, reservoir seal and hydrocarbon charge. Uncertainties lies even with the cost related to production of oil, oil cost in market and expectations are high of producing oil which is economically viable. In most of

Figure 1: Conventional Vertical Drilling

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Horizontal Drilling: Horizontal drilling was started in 1929 and became a common and prominent process by 1980s.The process of drilling in which the well is turned horizontally at a certain

Figure 2: Horizontal Drilling

depth after the conventional drilling process is called horizontal drilling. It takes a J shape. The point at which the vertical well deviates from its path at certain inclination to make it horizontal is called kick off point. The drilling of a horizontal well is much more complicated than drilling a vertical well. The driller has to calculate the approximate location above the point at which the drill must turn as that the existing drill assembly is removed and a special bit is installed for horizontal drilling. Directional Drilling: The process of controlling the direction of wellbore to guide it to a predetermined underground location baring oil is call directional drilling. Snake wells comes under the process of directional drilling. This is done using complicated tools, machinery and BHA. The paper further tells how it is done and more information about it.

Figure 3: Directional Drilling (Snake Drilling)

History and Development :

The snake well drill technique is first implemented in the champion west field offshore Brunei. This field was first discovered by the British Malayan Company which is now called as Brunei Shell Petroleum (BSP) which gave the term snake wells referring to the series of the wells (precisely 16 and 13 side-tracks) drilled over there. The first Field Development Plan was written in the year 1991 and in the end of 1990s and around 1997, shell started to make use of the development of new technologies in communication for data transmission and soundings for measuring and control automation for making decisions.  And also improvement in technology is reservoir imaging, which is to see what is happening underground and much more accurate drilling methods. In the start of the Drilling of the field it was very tough, complicated and expensive. Only 3 out of 5 planned drills were able to complete in the Phase 1 which led to postpone and reschedule the next subsequent phases. In the year 2000 the early oil campaign added 5 x 106 m3 of new oil reserves with daily average production of 2.5 to 3.0 x 103 m3  oil and 2 x 106  mln m 3. A full review of Champion west field was carried out in the month of September 2000. And in the year 2002 there was call for another field development plan for 6 oil and 2 gas wells were planned in the year 2003/4. In the phase 2 developments it includes the surface top deck extension to well jackets, piling new 36” and 30” conductors for single and splitter wellheads, installation of Containerized Electrical Room (CER), installation subsea power cable. This Phase 2 campaign took place in 2003 and 2004. Need for Snake Wells:

The concept of snake well is first given by Shell oil and first formulated in Rasau and later in Brunei. These well drilled along horizontal direction using extended reach drilling moving in a pattern comparable to a sinusoidal wave moving through multiple layers of shale within reservoirs. This concept have enabled fields once dormant to be produced economically. These wells tap into small and thin reservoirs while at the same time allowing the measurement and flow of separate sections. They are designed in such a manner to improve rate of production with continuous monitoring and controlling of each section with the smart completion methods. Due to its length, it is able to achieve maximum reservoir drainage and able to reach uneven horizontal surfaces. It terminate the need of multiple factors essential in the conventional method for various geological structures during drilling.

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 Along with the points mentioned above the design of snake well have following advantages:   

Its production efficiency is equal to the efficiency of 4-5 conventional well They do not require wellbore access for well management Their design drain multiple vertically stacked dipping reservoirs helps to form a common drainage pattern

With smart completion method, its design shows some unexpected benefits like minimizing subsurface uncertainties and cleaning up of well.

Working Of Snake Wells:

Snake wells is the terms used to represent the series of the horizontal wells which have been drilled in the Champion West field due to their peculiar structure in contrast to conventional Vertical drilling. In the other words it is the practice of directional drilling which means the drilling of Non vertical wells. This ground breaking piece of technology is very much useful in reaching the specific pockets of oil and gas traps or more precisely targets which are placed in the regions which are conventionally not reachable, environmentally sensitive areas where rig cannot be setup due to its ability to drill sideways. These non-vertical wells are drilled by simply pointing the drill in the required direction. There is a downhole steerable mud motor to which the drill bit is attached and there is bending near the bit and this bend steers the bit in different from wellbore axis. This mud motor turns only the bit instead of the complete length of drill pipe. When the required angle is achieved the drill string including the bend are rotated ensuring there is no other sideway drilling from wellbore axis. A probe full of instruments are placed in the drill pipe above the mud motor which enables the driller on the surface to get to know which direction and the what is the inclination he is heading. The probe that is being used is called MWD which means Measuring While Drilling. There are various logging sensors available which help in this geo steering.

Figure 4: Components of BHA

Most of the horizontal wells which are being drilled are based upon the reservoir and geological parameters and here we use the same parameters like in the regions with more porosity leads to higher ROP and any change in this ROP helps us to know that there is porosity change and so the well path is steered to maintain the high ROP or simply keeping the well path within the high porosity region. There are often many other logging tools that help us to sort out the horizontal drilling. Gamma Ray MWD tools are used to pick up the top of the reservoir. This is used while drilling the horizontal to provide assistance in lithological interpretations of layered or thin reservoirs.

Champion West Oil Field Overview:

Brunei Shell Petroleum has 7 offshore oil fields in which one of them is Champion Field. The country’s production of the oil reached a peak of 250,000 b/d and fell to 150,000 b/d in the nineteen eighties. Again it rose to 162,000 b/d and then to 180,000 b/d in 1992 and then falling to 174,000 b/d in the year 1993. On this same rate of extraction the country’s oil reserves wouldn’t last for more than 27 years’ time. The Champion west Oil Field which was discovered in the 1975 got the name in the year 1990. There are more than 1000 reservoirs in the champion west area. The geological location of the field is located in the north of the Brunei Offshore sector approximately 90km from Seria and some 10 km northeast of Iron Duke Field where the water depth is almost about 40 to 47 meters

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platform using Smedvig’s tender assist rig  West Pelaut. The wells have shown excellent initial flow rates with the start-up producer flowing at almost 17,000 b/d, or 2,650 cu m/d. This eclipses BSP’s record for a singl e well of 1,750 cu m/d achieved from Champion well. Henderson attributes CW-29’s high reservoir deliverability to its snake trajectory and optimized completion design. Champion West completion has two zones, each controlled by variable interval control valves (ICVs) to balance the offtake from either zone. Each zone has two pressure gauges associated with it on either side of its valve - one to measure reservoir pressure, and one to measure pressure inside the completion.

Smart Completions: . Figure 5: Location of Champion West Field 

The champion west field consists of about 1200m vertical reservoir sequence over a complete area of 10km2 in 15 main blocks. The hydrocarbons have been found over a wide stratigraphic range which consists of number of distinct columns of thick shale along with accumulation of thin shales. This formation sequence then continues into gas prone as the depth increases. This gas is either present as either associated or non-associated gas. The column length of oil varies from 22 to 400 meters. The field development was divided in to different phases. The phase 1 and phase 2 developments are discussed in the history and development where the initial phase was tough to start with and also expensive. In the later phase there was installation of Containerized electrical room, single and splitter wellheads and in this phase 6 oil and 2 gas wells were planned to drill. In the Phase 3 development, there are 20 wells including of both oil and gas. In this phase there is implementation of ERD wells in which they are designed as “snake” wells which penetrate into the reservoir several times. They found that, due to the complex nature of vertically stacked and structurally dipping reservoirs there is a very need for a well design which is different from the standard design. The vertical drilling method was already ruled out, multilateral drilling concept was also not considered taking into the account of cost and complexity, conventional horizontal drilling concept was not attractive because there would be need for more number of wells required for reservoir drainage. So the ultimate design required to rule out all the complications is to drill in shape of snake horizontal wells with “Smart Completions” Phase 3 of Champion West is actually split into three sub-phases - the 3a, initiated in 2004, involves drilling five development wells from a newly installed

The main difficulty with these kinds of wells lies in their completion which means making the well to produce the oil. To achieve the completion, dogleg severity needs to be controlled and directional tools are required. According to the Project leader Grahaeme Henderson the snake wells had given positive end results with low unit development costs, high initial flow rates and also that recovery efficiency has been proved to be significantly better than many cases of vertical wells. To obtain a perfect or optimized completion the completions must be smart which imply the usage of Flow control valves, Pressure gauges, fiber optic temperature sensors which will be operated remotely. By this design the will be no need for well bore access for well or reservoir management and for its maintenance. This platform provides remote access to BSP’s operation center in Seria via high band width connections to the shore which helps in conducting the real time monitoring, clean up and optimization of wells. Also helps in online testing of the well using multiphase flow meter and Rapid shut down and start up whenever required. It also allows production testing of individual zones without interventions and with minimal production interruption. The well is also equipped with a fibre-optic distributed temperature sensor to monitor its clean-up and in-flow behaviors, and to detect early signs of gas and/or water breakthrough in the future. There is also a room for increasing the economic life span of the wells. Initially used in subsea wells, where intervention is expensive and high-risk, intelligent completions have since proven their value in managing production from multilateral wells, horizontal wells with multiple zones, wells in heterogeneous reservoirs, and mature reservoirs. According to the Henderson, many of

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BSP’s wells off Brunei have been optimized using smart field technologies.

There are three types in the horizontal drilling based on the radius of curvature where the wells with short radius have inclination of 2 to 60 / 30 m of horizontal displacement, Medium radius wells with 8 to 200 / 30 m and extend up to 1000 m or more. Much advancement in this horizontal drilling has been made and this technique is being incorporated in all the situations, but it also has its weakness like casing design and cementing problem many horizontal wells are completed as open hole. The casing for this type of drilling we need to know the loads applied on the casing string. The horizontal drill trajectory clearly shows the well is divided into three intervals: horizontal, build up section, vertical section. All these different sections have the different loads applied on them. Horizontal section-

The calculations are done for 5”, 7”, and 9” with coefficient of friction 0.2 to 0.4 and found the load for casing having weight 18lb/ft.

This gives that we need to push at the build-up section for both “open and closed end Casing” because there is huge load which can damage the casing so it should be considered.

Build Up SectionIt changes both in direction and inclination which implies it has drag and bending loads on the casing. Their inclination varies from 5 to 50o per 100 feet and the load is mostly compressive and it iv=creases with the increase in the horizontal section Vertical Section-

This section of the well is almost horizontal with 80 to 900 inclination with vertical. The section is subjected to torque and drag forces which are the result from the contact of the pipe to bore hole. Two factors affect sliding wellbore friction which is coefficient of friction and normal contact and their product gives magnitude of friction force (2). The value of the sliding friction depends on the contacting material and degree of lubrication at various places.

The load is maximum at the starting of the well bore and it is equal to the weight of the casing string and the load at kick off point. Drawbacks of Snake Well Design:

Snake well has shown significant improvement in the production or recovery of oil from the reservoirs and in some cases, even better than vertical drilling. During its implementation, challenges regarding its placement and control of the wells occurred due to its completely new design but smart completion method tackled the challenges easily with the advanced flow control valves, sensors and other productive tools. The challenge related to dismantling and reassembling equipment were easily brought down by using mobile drilling units moved between pads which automatically brought the cost down by 10-20%. In spite of all the challenges and limitations occurred and solved, The present day design of the snake well still contains flaws and drawbacks leading to high risk and uncertainty. Some of the drawbacks related to its design are: 

Figure 6: Horizontal Section

From the figure it is clear that Ft = W cosØ + µ Fn Torsional increment

ΔM=µ*Fn*r 

Missing of Target Zones The design of snake well uses extended reach drilling with directional drilling technique moving like a snake increase the risk of accidentally miss the target zone due to geological uncertainty and may hit the neighboring water bearing zones, decreasing production of oil.

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Non Unique Log and Data Interpretation Since the snake moves through the complex horizontal path cutting different layers of shale packages through the reservoirs increase the chances to get stratigraphically lost due to nonunique logs.

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Condition of Hole with Time  Although the use of smart completion methods has helped to maintain the well clean but up to few meters and beyond that, the well hardly get cleaned and the toe hardly contributes to the flow rather increase the hindrance.

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Breakthrough of Water/Gas at Heel  At initial stages, due to the difference in size of toe and heel during the drawdown there is a high risk of breakthrough of water or gas which lead to decrease the formation pressure and ultimately lead to decrease in the production

Proposed techniques for Improvi ng the Oil Extraction percentage:

1.In snake drilling technique, there is a probability that the drill bit misses the exact target location and may hit the adjacent water containing sandstone or geological uncertainty leading to the decrease in the production of oil. Hence the following method is proposed to reduce the chances of this to happen.  All of the horizontal wells drilled are done taking into the account of geological parameters of the formation. We can steer the well using the geological information we get from the drill bit cuttings which comes out with the mud. This helps us know that the drill bit had hit a zone of sand or gravel. Also we get to know through the rate of penetration in the particular formation. For example, the rate of penetration in porous formation is more than that of hard formations. That means the ROP changes depending upon the type of formation encountered. So for the drill bit not to get accidentally enter into neighboring water bearing zones we previously get the information about the type formation we have entered. For this we implement Schlumberger iPZIG system. It is image Gamma and an inclination tool positioned directly behind the bit. It reduces the reaction time for making the critical geo steering decisions and maintaining the wellbore in the targeted region. Hence it helps in maintaining the original well trajectory without allowing the drill bit to enter other unnecessary paths. Thus, this would result in no loss of percentage of oil. The chance of the drill bit to hit a water bearing layer can be predicted by sudden thinning of the drilling fluid, dropping of the water temperature, drop in level of drilling fluid and sudden increase in speed of drilling.

2. Sometimes the previously isolated or separated fluid or some other fluids which are present in the formation gets access to the producing wellbore mainly water and gas. These cause a serious problem which would lead to decrease in the formation pressure and leads to greater decrease in the production. This interruption of unwanted well fluids such as water and gas shows its impact on wells and its reservoir performance. In addition to this there might be also a sand inflow into the ICD. Simple sand control is not enough the flow control must also be done together to maximize the oil production. To accomplish this task we equip MeshFlux with special inflow control devices which are places along the production intervals to equalize the production from toe to heal. MeshFlux integrates meshrite which works under nozzle based flow control. The reservoir fluid first passes through the meshrite sand control medium and then along the outside of the base pipe to the nozzles’ at the end of the base pipe. These nozzles which are viscosity independent help to equalize the pressure from the heel to toe inside the pipe the helps in the influx of oil. In case of homogeneous formations, the oil which is at high pressure tends to enter the heel of ICD which is at low pressure creating damage to the toe. But as the mesh flux ICD helps to equalize the pressure from the heel to toe that helps in entering of oil into ICD equally. Concluding Remarks:

Hence Snake well drill technology increases the production and decreases the cost of production. In case of the Champion West Oil field in Brunei there is an increase of 300 billion barrels of oil due to the introduction of the snake drill technology. The proposed methods would eliminate the drawbacks of this kind of wells and should help in the improvement of the oil extraction percentage from the drilled snake wells.

Nomenclature:

BSP: Brunei Shell Petroleum CER: Containerized Electrical Room ROP: Rate of penetration MWD: Measuring While Drilling  AND: Azimuthal Density Neutral Tool CDR: Compensated Dual Resistivity Tool ICD: Inflow control Device

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References:

1. absolutetect.com/flowcontrol/meshflux 2. Combination of Snake Well Design & Smart Completions: Key Enablers for Champion West Development. SPE 88524. Aidiradiman Haji Johan (Brunei Shell Petroleum Company Sdn. Bhd) kirby Schrader (Brunei Shell Petroleum Company Sdn. Bhd). 3. Pehin Dato Haji Mohammad, Minister Of Energy , Brunei “Development And Environment”

 Au th or Con tac t Det ail s 

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B Sreeranga Pradyumn a Mobile: 8171949239 Email: [email protected]

G Sai Akhil Mobile: 9505145382 Email: [email protected]

 An ku r Dw iv edi Mobile: 9807029205 Email: ankurdwiv [email protected]

4. “editions.sciencetechnologyactions.com/lessons2 21616.php”

5. “Smart snake wells in champion west -Expected and Unexpected Benefits from Smart Completion” SPE 100880, W.Obendrauf, K.Schrader, N. Al-Farsi and A. White, SPE, Brunei Shell Petroleum Co. Sdn. Bhd. 6.www.glossary.oilfield.slv.com/terms/breakthrough.aspx