The Na Kika offtake guidelines were developed jointly by Shell and BP using a blending of recent sand control operational methodologies from each company.In this paper, we focus on the use of the bpfluxTM guidelines, which give the maximum safe operating rates for sand control completions, and allow wells with excellent completion quality to produce at twice the rate of wells with lower completion quality. Before the Na Kika field started up, we estimated the completion quality by reviewing 20 different elements of completion design and operations.We used these estimates to set the initial off-take limits for each zone.As the wells started producing, we performed pressure build-ups to measure the actual completion quality (skin), and adjusted the maximum operating rates accordingly. Using this methodology early in field life, we were able to bring the field up to targeted production rates without unnecessarily compromising long-term sand control reliability.As the field matures, we will identify opportunities to extend the production plateau, which will provide an incremental production impact.Finally, later in the field life, we also expect to lower the number of workovers, which will provide an additional cost savings from using these guidelines. Introduction The Na Kika development is in the deepwater Gulf of Mexico (Figure 1), with 12 subsea wells that tie back to a host facility with a production capacity of 130 MBOPD and 500 MMCFD.There are six separate fields that tie-back to the host, which makes this development unique because there is no large field that justified the host on a stand-alone basis. With the exception of the Coulomb field, which was developed after the scope of work in this study, Shell and BP are equal partners in the Na Kika development.All the wells have sand control completions, two are open-hole horizontal wells with gravel packs, and the remaining 8 wells are cased holes with frac packs.As with any deepwater and sub-sea development, long-term reliability of each well is critical to the project success. Over the past few years, sand control well operating guidelines have moved away from drawdown based limits and are now based on velocities at various locations in the completion.In particular, two recent works both offer powerful new methods for safely operating sand control completions.Wong et al[1] discusses two velocity limits; one is the perforation velocity at the casing inside diameter, which that leads to destabilization of the annular pack.The second is the velocity at the surface of the screen and causes screen erosion failure.They also present a surveillance tool methodology to monitor well clean-up during the start-up portion of a well's life.
A pilot test of an integrated sand and erosion alarming process has been implemented in the NaKika field, in the Gulf of Mexico. All wells have sand control completions. Except for one well with a gravel pack completion problem, all the other wells are controlled by a flux limit (SPE Paper 84495). A Microsoft Excel based program was developed to automatically receive daily morning report data, and perform nodal analysis calculations on all of the wells, in order to estimate: mechanical skin corrected for relative permeability changes, pressure drawdown, gravel pack flux, and wellhead velocities. The wellhead velocities were utilized to calculate erosion rate to estimate metal loss. Corrosion rate at the wellhead was also estimated. All calculated results are sent to OSI PI as data tags and viewable through a commercial real time trend-analysis program. The Excel program results are also automatically emailed to the engineers. The gravel pack flux limits are used to make sure we do not produce the wells at rates which increase the probability of sand control failure. Monitoring of the flux results were subsequently used to increase the gas rate of one well by 15 MMSCF/D, and an oil well by 4.8 MBOE/D. Wells were ramped up in a controlled manner via programmable logic controllers. Acoustic sand detectors showed very little sand production, primarily during ramp up. The controlled ramp up is believed to be the most important reason that we have not observed any sustained sand production. After a year of operation, we have had only one minor separator cleanup for sand, most of which has been proppant from double and triple frac packs. Introduction BP produces from the NaKika host a collection of oil and gas fields in 6300 ft of water in the Gulf of Mexico. All wells were developed with sub sea completions. The various oil and gas wells produce from the Miocene age sands. There are ten wells, seven that produce from oil bearing sands, and three that produce from gas sands. Individual oil wells produce as much as 35,000 STB/D, and one gas well has produced as much as 168 MMSCF/D. The formations are prone to produce sand. Eight of the wells are completed with frac pack completions. In some cases, there are double frac packs with sliding sleeve completions, and in three wells, there are three commingled frac packs. Two wells are horizontal with open-hole gravel packs. One of those wells failed to have all of the sand placed behind the screen. The nine wells with good frac pack and gravel pack completions were limited by the flux through the gravel pack. Tiffin et el1 discussed how oil and gas wells with sand control can be controlled by monitoring flow through gravel pack screen to minimize the risk of screen erosion. Tiffin et el1 reported that a high frequency of screen erosion failures occurred when the flux exceeded 60, and no failures occurred below 60. The well with a poorly executed gravel pack completion was draw-down limited. Oil and gas fields that produce sand can have erosion at the wellheads, wellhead chokes, wellbore restrictions, and topsides. A common practice is to perform erosion calculations for the maximum expected velocities through various piping. Corrosion can be made worse in sand prone environments because erosion and corrosion can work together to yield greater metal loss. While the tubing and wellhead metallurgy is 13 chrome steel, carbon steel is used immediately after the wellheads.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA pilot test of an integrated sand and erosion alarming process has been implemented in the NaKika field, in the Gulf of Mexico. All wells have sand control completions. Except for one well with a gravel pack completion problem, all the other wells are controlled by a flux limit (SPE Paper 84495).A Microsoft Excel based program was developed to automatically receive daily morning report data, and perform nodal analysis calculations on all of the wells, in order to estimate: mechanical skin corrected for relative permeability changes, pressure drawdown, gravel pack flux, and wellhead velocities. The wellhead velocities were utilized to calculate erosion rate to estimate metal loss. Corrosion rate at the wellhead was also estimated. All calculated results are sent to OSI PI as data tags and viewable through a commercial real time trend-analysis program. The Excel program results are also automatically emailed to the engineers.The gravel pack flux limits are used to make sure we do not produce the wells at rates which increase the probability of sand control failure. Monitoring of the flux results were subsequently used to increase the gas rate of one well by 15 MMSCF/D, and an oil well by 4.8 MBOE/D. Wells were ramped up in a controlled manner via programmable logic controllers. Acoustic sand detectors showed very little sand production, primarily during ramp up. The controlled ramp up is believed to be the most important reason that we have not observed any sustained sand production. After a year of operation, we have had only one minor separator cleanup for sand, most of which has been proppant from double and triple frac packs.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Na Kika offtake guidelines were developed jointly by Shell and BP using a blending of recent sand control operational methodologies from each company. In this paper, we focus on the use of the bpflux TM guidelines, which give the maximum safe operating rates for sand control completions, and allow wells with excellent completion quality to produce at twice the rate of wells with lower completion quality.Before the Na Kika field started up, we estimated the completion quality by reviewing 20 different elements of completion design and operations. We used these estimates to set the initial off-take limits for each zone. As the wells started producing, we performed pressure build-ups to measure the actual completion quality (skin), and adjusted the maximum operating rates accordingly.Using this methodology early in field life, we were able to bring the field up to targeted production rates without unnecessarily compromising long-term sand control reliability.As the field matures, we will identify opportunities to extend the production plateau, which will provide an incremental production impact. Finally, later in the field life, we also expect to lower the number of workovers, which will provide an additional cost savings from using these guidelines.
Summary The Na Kika offtake guidelines were developed jointly by Shell and BP using a blending of recent sand control operational methodologies from each company. This paper focuses on the use of the BpfluxTM guidelines, which give maximum safe operating rates for sand-control completions and allow wells with excellent completion quality to produce at twice the rate of wells with lower completion quality. Before the Na Kika field started up, completion quality was estimated by reviewing 20 different elements of completion design and operations. These estimates were used to set the initial offtake limits for each zone. As the wells started producing, pressure buildups were used to measure the actual completion quality (skin), and the maximum operating rates were adjusted accordingly. By use of this methodology early in the field life, the field could be brought up to targeted production rates without unnecessarily compromising long-term sand control reliability. As the field matures, opportunities will be identified to extend the production plateau, which will provide an incremental production impact. Finally, later in the field life, the number of workovers required is expected to be reduced, which will provide an additional cost saving from using these guidelines. Introduction The Na Kika development is in the deepwater Gulf of Mexico (Fig. 1), with 12 subsea wells that tie back to a host facility with a production capacity of 130,000 barrels of oil per day (MBOPD) and 500 million cubic feet per day (MMCFD) of gas. There are six separate fields that tie back to the host, which makes this development unique because there is no large field that justified the host on a standalone basis. With the exception of the Coulomb field, which was developed after the scope of work in this study, Shell and BP are equal partners in the Na Kika development. All the wells have sand control completions, two are openhole horizontal wells with gravel packs, and the remaining eight wells are cased holes with frac packs. As with any deepwater and subsea development, long-term reliability of each well is critical to project success. Over the past few years, well operating guidelines for sand control have moved away from drawdown-based limits and are now based on velocities at various locations in the completion. In particular, two recent studies both offer powerful new methods for safely operating sand control completions. Wong et al. (2003) discuss two velocity limits: one is the perforation velocity at the casing inside diameter, which, if too high, leads to destabilization of the annular pack. The second is the velocity at the surface of the screen, which if too high, causes screen erosion failure. They also present a surveillance-tool methodology to monitor well cleanup during the startup portion of a well's life. Tiffin et al. (2003) present the results of a large database used to develop empirical guidelines for safe operation of sand-control completions. They introduce a flux-based c-factor, which is directly proportional to the perforation velocity and allow wells with excellent completion quality to produce at twice the rate of wells with unknown or poor completion quality. The focus of this paper is on the application of these BpfluxTM guidelines to the Na Kika development. This paper begins with a brief overview of the BpfluxTM guidelines, highlighting the importance of a high-quality completion. It proceeds to discuss how these guidelines were incorporated into the Na Kika offtake guidelines. Two planned pressure buildups performed early in the well life to document the skin for each well are discussed and analyzed. The paper continues with examples of the use of pressure buildup (PBU) results and actual well drawdown data to increase the rates of wells using the guidelines. Use of these guidelines during the life of the field, particularly for wells with increasing skin, is also discussed. The paper concludes with a review of the actual Na Kika completion quality, examining which elements of the completion design and execution correlate with the measured skins. BpfluxTM Overview The BpfluxTM guidelines were developed by (Tiffin et al. 2003) using an extensive database of cased-hole and openhole sand control completions, primarily from the Gulf of Mexico and Trinidad. The rationale for developing these guidelines is made clear in Fig. 2, which shows the fate of 160 wells in the database. The vertical axis is the total drawdown, and each vertical colored bar represents a well. Green-colored wells had no sand production, yellow wells produced some sand, and red wells were erosion failures. Only wells with confirmed good-quality completions were included in the database; early-life failures caused by poor sand-control placement were excluded. First, Fig. 2 shows that there is no correlation between drawdown and well failures. Several wells with drawdown over 1,500 psi operate with no sand production, while one well with only 250 psi drawdown failed. Even the average values show no correlation, as the average drawdown of wells that failed is approximately 50 psi lower than the average for wells that produced sand-free. These observations led to the development of the BpfluxTM guidelines for cased-hole sand control completions, which are illustrated in Fig. 3.
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