As gas fields mature and water production increases, understanding and managing the dynamic flow behaviour of the well and production system are critical for maintaining, and even optimising, production. This knowledge could be the difference between a successful and an unsuccessful attempt at re-starting a wet gas well after it is shut-in. When a well is in production, choking the well to optimise stable facilities operation and maintain water production within the water handling constraints of the facilities can be a fine line between achieving continuous stable production and the well ceasing production due to high liquid loading.
This paper describes the successful kick-off and unloading of two high-water producing gas wells within the operational constraints of the offshore facility. Transient multiphase flow models were developed for a platform well and a subsea well to simulate the wellbore flow dynamics during start-up. The models were tested over a range of values for parameters such as reservoir pressure, inflow performance and water gas ratio for different kick-off strategies but always honouring the facility's water surge management constraints.
The outcome of these simulations facilitated the development of tailored bean-up strategies for each high-water producing gas well, which provided a mechanism to engage with key stakeholders and demonstrate confidence in the execution of these strategies. Dedicated procedures were developed and subsequently executed successfully to re-start the two wells with the wells continuing to produce after kick-off and unloading, operating within the water surge management limits of the facility. Similar strategies are being developed for other high-water producing gas wells including those with material sand production.
This paper demonstrates strategic capability to realise additional value using dynamic modelling to kick-off mature high-water producing gas wells through proactive development of mitigation strategies which avoid production disruption.
The Barents Sea offers unique drilling challenges related to issues such as biogenetic gas in shallow formations, thermogenic gas seeps up to the seabed from underlying formations, shallow formations with abnormal pressure, shallow reservoirs, low-fracture-pressure formations in part of the overburden, and naturally fractured/karstified carbonate reservoirs. This paper discusses cementing challenges when drilling wells in the Barents Sea and the experience gained using managed pressure cementing (MPC) practices.
When drilling the surface hole in potentially slightly overpressured formations, the riserless mud recovery (RMR) technique was used. For the first time on the Norwegian Continental Shelf (NCS), MPC was used when cementing the surface casing. RMR compensates for drilling the overpressurized zones without a riser and blowout preventer (BOP), and MPC allows for pressurization and monitoring of the pressure on the subsea wellhead toward the formation during the cement curing stage.
Once the marine riser and BOP were installed, controlled mud level (CML) technology was used during drilling, running casing/liners, cementing operations, and other activities. CML enables manipulation of the fluid level in the riser and therefore helps optimize downhole pressure to avoid losses and maintain an overbalance. CML has proven to be particularly useful during cementing of liners in naturally fractured reservoirs and during setting of balanced cement plugs in an open hole. As a result, high circulation rates can be achieved and conventional high-density cement slurries can be used.
MPC using either RMR or CML was employed for the first time in the Barents Sea. Examples of how cementing operations were planned and executed are described and results are presented.
Alchibaev, D. V. (OOO Gazpromneft NTC) | Glazyrina, A. Ye. (OOO Gazpromneft NTC) | Ovcharenko, Yu. V. (OOO Gazpromneft NTC) | Kalinin, O. Yu. (OOO Gazpromneft NTC) | Lukin, S. V. (OOO Gazpromneft NTC) | Martemyanov, A. N. (OOO Gazpromneft NTC) | Zhigulskiy, S. V. (OOO Gazpromneft NTC) | Chebyshev, I. S. (OOO Gazpromneft NTC) | Sidelnik, A. V. (OOO Gazpromneft NTC) | Bazyrov, I. Sh. (Saint-Petersburg Mining University)
For the prediction and elimination of complications in the drilling process is considered a number of examples of the three-dimensional geomechanical model and of the near-wellbore model in order to optimize the trajectory and design of the wells. During the well trajectory planning, the key point is to forecast and minimize all possible risks associated with both geological, mechanical conditions and technological parameters. An optimal solution can be obtained with the use of a detailed geomechanical analysis.
It is shown that in a number of cases, the numerical model of the near wellbore zone is more informative, in comparison with the analytical solution. The result of drilling risks minimization with help of geomechanical analysis tools is presented. A number of recommendations on wellbore construction and stability are established of the comprehensive geomechanical analysis. The discontunities that are derived of seismic field analysis are also included in the review.
The image analysis, 1D geomechanical modelling, of seismic field analysis, near-wellbore numerical simulation and full 3D goemechanical modelling were used as a geomechanics tools to optimize "fishbone" trajectory. Microimages help to determine the presence of cavernousness, natural and induced fractures, geological boundaries and bedding planes. Especially useful is a tool for determining the presence of collapse in the areas of kick-off sidetracks. 1D geomechanical modeling helps to determine favorable intervals for shearing and optimal mud density. To assess the risks during the sidetracking operation, a statistical analysis of the actual data was carried out taking into account the spatial orientation of the sidetrack and the direction relative to the currently acting stress state. Stresses and gradients of caving in the intervals of cuts are refined by the near wellbore model.
Hussain, Sajjad (Schlumberger) | Dhaher, Karam Sulaiman (Schlumberger) | Bjoerneli, Hans Magnus (Schlumberger) | Blackburn, Jason (Schlumberger) | Monterrosa, Leida (Schlumberger) | Jakobsen, Tom (Statoil ASA) | Otto Monsen, Gisle (Statoil ASA) | Haaland, Sigurd (Statoil ASA) | Dahl, Johan (Statoil ASA) | Østensen, Ståle (Statoil ASA) | Fjelde, Kjell Kåre (University of Stavanger)
AbstractOld platforms are not well known for extended-reach drilling (ERD) operations mainly due to rig and hydraulics limitations. ERD wells demand robust rig capabilities, good hydraulics systems, and equipment reliability. In addition, the well profile, rotary steerable system (RSS), measurement-while-drilling (MWD) and logging-while-drilling (LWD) tools, surveying, and new technologies are extremely important to the success in drilling an ERD well. RSS and drillpipe selection are important factors for hydraulics optimization. Surveying techniques are also important for time saving and improved efficiency. An ERD well in the North Sea Statfjord field was kicked off in the 17 ½-in. section from the openhole cement plug through a 50-m window between the 20-in. casing shoe and 13 3/8-in. casing stump, ensuring a smooth well profile and reduced doglegs compared to the whipstock window exit. The 17 ½-in. section was drilled and landed at a 79° inclination using point-the-bit RSS technology, and the 12 ¼-in. section was drilled in two runs as planned using the point-the-bit RSS withstanding more than 550 h down hole. The 9 5/8-in. liner was run and floated successfully in the ~6000-m section. Strict adherence to surveying techniques and quality control processes proved very helpful to meet Operator technical requirements. The 8 ½-in. section was drilled and landed on top of the reservoir with an inclination decrease from 88° to 35°. New MWD technology was successfully used in drilling the 6-in. section. These latest technologies as well as employing appropriate techniques help to drill ERD wells on aged platforms like those in the Statfjord field. This paper will describe the planning and execution phases of a challenging ERD well drilled in the Statfjord field.
Ab Hamid, Abdul Halim (Saudi Aramco) | Siregar, Verdy (Saudi Aramco) | Khalil, Mohamed E. (Saudi Aramco) | Ghazzawi, Ayman (Schlumberger) | Ashraf, Omar T. A. (Schlumberger) | Balka, Muhammad S. (Schlumberger)
Generally, deep gas workover/re-entry wells in Saudi Arabia are kicked off in the Sudair formation through a whipstock because the overlying base Jilh dolomite can flow with high pressure, which jeopardizes well control. Whipstocks are set deep in the 9 5/8-in. casing, after which the 8 3/8-in. and 5 7/8-in. holes are drilled to access the target Lower Carbonate and Sand reservoirs. Deeper kickoffs also avoid contact across the water-bearing Carbonate A, aiming for displacement across Carbonate B or C reservoirs. Isolation from Carbonate A is important for multistage fracturing completions as they are still not proven for the long-term isolation of water-bearing zones.
Regardless of the deeper whipstock setting, the high dogleg requirements exceed the capabilities of conventional rotary steerable systems (RSS). Conventional steerable motors with high-bend housing and 70 to 80% of the sliding mode of drilling has been the only option to achieve such high dogleg severity (DLS/100ft). Drilling medium-radius wells with a conventional motor assembly requires multiple runs, wiper trips to clean the hole, and multiple reaming trips before running the liner. These operations result in poor drilling efficiency due to slow penetration rates and bit trips.
A high build rate rotary steerable system (HRSS) was introduced as a solution for such challenges in the 8 3/8-in. and 5 7/8-in. sections. While the HRSS technology has been used before, this was the first time the HRSS kicked off vertically from a whipstock in Saudi Arabia or worldwide. The new technology allowed the kickoff point to be pushed further into the Sudair formation near the Sudair dolomite, reducing the risk from Jilh pressure and associated cost. The step change provided the option to slim the hole by eliminating the 8 3/8in. hole size, and kickoff was done in the 7-in. liner. Deployment of the HRSS allowed directly kicking off from a whipstock set vertically, eliminating the need for a dedicated steerable motor assembly run. Direct kickoff also meant eliminating the need for gyro tool for steerability, because conventional RSS tools could only be used outside the zone of magnetic interference, once sufficient separation from the mother bore was achieved. Consistent doglegs of more than 14°/100 ft were recorded; and the maximum dogleg was 17.44°/100 ft. Since then, this concept has been applied to other vertical re-entry wells and at an existing inclinations successfully in the 8 3/8-in. and 5 7/8-in. sections in Saudi Arabia and worldwide. The scope of the paper is limited to wells in Saudi Arabian deep gas wells only. The average rate of penetration (ROP) across this build section shows a 137% improvement over the ROP for conventional motor bottom-hole assemblies (BHA) for similar build sections. Eliminating the 8 3/8-in. section, avoiding the hazards of drilling in Jilh and Sudair formations, saving the motor trip to kick off from the whipstock, and improving ROP resulted in significant savings. This step change in drilling performance was realized by a thorough understanding of local drilling conditions and indepth analysis that enabled efficient execution.
VICO Indonesia is an Oil and Gas company which has operated mature fields located in the onshore part of East Kalimantan which has been on production for over 30 years. The fields are dominated by gas reservoirs with a much lower presence of oil reservoirs. Production mechanisms cover from natural depletion to weak and strong water drive, particularly in some of the shallow areas. Recent well completions include single and dual slimhole monobore.
The field is a perfect combination of stratigraphic and structural traps with more than 4000 sandstone reservoirs where around 450 of those are oil reservoirs. The oil recovery factor for these reservoirs is in the range of 10-30%. Oil development in this fields performed using gas lift as the main artificial lift while several wells still flowing naturally. Coiled tubing gas lifted (CTGL) wells contributes to 60-80% of current oil production of 8000 BOPD.
Totally, 50 CTGLs have been installed in VICO Indonesia where most of those considered successful. The main problem found related with initial operation after installation. Lesson learned has been summarized including the design and the procedure for initial operation. Coiled tubing gas lift design and troubleshooting are rarely found in literature. Thus, this paper presents the detail step by step design and how to troubleshoot the possible failure during early operation. This approach exhibits a real benefit to recover more untapped hydrocarbon with more aggressive program.
Setting cement plugs for sidetrack operations is a critical, challenging, and time-consuming operation. In many cases, a successful sidetrack operation requires several cement plug attempts or lengthy drilling operations, resulting in increased operation cost. In the past, when required to sidetrack a well, cement kickoff plugs were regularly tagged without having achieved the desired compressive strength, with added risk of stuck pipe in soft cement and increased wait-on-cement (WOC) time. The poor cement plugs usually resulted in a time drilling operation after additional WOC time. Placing a successful kickoff-plug (KOP) consistently on the first attempt is required for a cost-effective sidetrack operation, which, by itself, is considered an additional cost to any drilling project. In the Awali field in Bahrain, drilling operations faced the challenge of increased loss time in KOP operations. Operator wanted to reduce WOC time by improving the performance of the cement KOPs. The target was to complete the sidetrack operation in well depths less than 3,000 ft and static temperatures of about 140°F within 8 to 12 hr, after the cement plug has been placed.
A thorough analysis of previous design and execution cement practices was performed to identify the actions needed to optimize the previous performance of cement plugs. Advanced cement plug optimization software was used to support the evaluation of the risks associated with the placement of the slurry. Data from extensive laboratory testing of several cement slurry systems were used to evaluate the effect of the slurry properties on optimizing the system deemed most suitable for this application. The studies also included a detailed review of the industry best practices that are applicable to the conditions of the field. The results of the implemented best practices for the design and execution of KOPs in shallow wells in the field under study demonstrated an improvement of the success rate to 100% and better cement plug performance, contributing significantly to minimizing the time and cost of performing sidetrack operations.
For stimulation of tight fields, alternatives to hydraulic fracturing based on hydraulic jetting are becoming available. With hydraulic jetting many (10 to 20) laterals can be created in a (sub-) vertical well. The laterals are 100 to 200 m long, typically 4 laterals are applied with a small inclination at a single kickoff depth. This type of well configuration will be called a radial well. A simulation tool based on a semi-analytical method is developed to computate the production performance of a radial well. The tool provides an efficient way to assess the production potential of a stimulated well for many different well designs. The method is particularly suitable for performing a sensitivity analysis to preselect a limited number of designs to be further analysed. The results of the tool show excellent agreement with those of a numerical reservoir simulator. As an example, the tool is applied to a stacked field with three separate reservoirs, wich have permeability ranging from 1 to 5 mD. The radial well increases cumulative gas production by 10% for the reservoir with 5 mD and by 50-70% for the reservoirs with 1 mD permeability.
When kicking off at low inclination, static measurement-while drilling (MWD) surveys are used to confirm the kickoff direction, when free of magnetic interference from offset wells. However, because MWD continuous azimuth and inclination measurements have limited accuracy when near vertical, the directional driller does not have confidence in the kickoff direction with continuous (dynamic) survey while drilling. This requires additional static surveys to be made, taking up rig time. In a novel continuous survey method used in a particular rotary steerable system (RSS), a six-axis survey was taken continuously, both while drilling and when static, with the survey sensors being housed in a rotation-speed-controlled platform in the RSS. This algorithm was first verified in a software simulator, and it was subsequently implemented in hardware and tested in a hardware-in-the loop (HIL)-simulator environment. The effectiveness of the new measurement method was field tested and compared with MWD static survey points. The field-test result shows that the new near-bit continuous azimuth and inclination measurement from the RSS is considerably more accurate than the MWD continuous measurements at very low inclinations less than 5°. The new survey method not only provided more-accurate kickoff from a near-vertical position but also enhanced the automated-vertical-drilling feature. In addition, improved continuous measurements around magnetic north and south allowed the closed-loop attitude-hold algorithm of the RSS to drill lateral sections more precisely in these directions. This unique measurement method has valuable applications, such as low-angle kickoff without the use of multiple static surveys because the directional driller can use the continuous azimuth and/ or tool face to accurately steer the well. Equally important is that if gyro surveys are required, their number will reduce when the survey-measurement point is so close to the bit, reducing the amount of time of exposure to magnetic interference from an offset casing. When drilling out of the shoe, this survey method will allow an accurate kickoff approximately 50 ft earlier than would normally be expected when magnetic interference is cleared. In addition, the use of a continuous gravity tool face (GTF) is possible without the need for static surveys, allowing accurate low-side sidetracks to be performed even in areas of high magnetic interference. This surveying method reduces the rig time needed to kick off and provides a more reliable real-time measurement for the directional driller to ensure that the desired well trajectory is drilled through crowded platform environments.
When kicking off at low inclination, static measurement-while-drilling (MWD) surveys are used to confirm the kickoff direction, when free of magnetic interference from offset wells. However, as MWD continuous azimuth and inclination measurements have limited accuracy when near vertical, the directional driller does not have confidence in the kickoff direction with continuous (dynamic) survey while drilling. This requires additional static surveys to be made, taking up precious rig time.
In a novel continuous survey method used in a particular rotary steerable system (RSS), a six-axis survey was taken continuously, both while drilling and when static, with the surveys sensors being housed in a rotation-speed-controlled platform in the RSS. This algorithm was first verified in a software simulator, and it was subsequently implemented in hardware and tested in a hardware-in-the-loop-simulator environment. The effectiveness of the new measurement method was field tested and compared against MWD static survey points. The field test result shows that the new near-bit continuous azimuth and inclination from the RSS is considerably more accurate than that of the MWD continuous measurements at very low inclinations of between 1° and 5°.
This unique measurement method has valuable applications, such as low-angle kickoff without using multiple static surveys as the directional driller can use the continuous azimuth and/or toolface to accurately steer the well. Equally important is that if gyro surveys are required, their number will reduce as the survey measurement point is so close to the bit, reducing the amount of time of exposure to magnetic interference from an offset casing. When drilling out of the shoe, this survey method will allow an accurate kickoff approximately 50 ft earlier than would normally be expected as magnetic interference is cleared. Additionally, the use of a continuous gravity toolface is possible without the need for static surveys, allowing accurate low-side sidetracks to be performed even in areas of high magnetic interference. This surveying method reduces the rig time needed to kick off and provides a more reliable real-time measurement for the directional driller to ensure the desired well trajectory is drilled through crowded platform environments.