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Collaborating Authors
Abstract Multi-stage matrix acidizing is a common stimulation technique applied in low permeability carbonate reservoirs to increase hydrocarbon production. Frac balls are utilized to activate stimulation sleeves to achieve pin-point stimulation. Frac balls used during each stimulation stage also help in isolating the already stimulated lower zones. However, subsequent milling interventions are required after stimulation to remove conventional composite or steel frac balls. Utilization of dissolvable frac balls eliminate the need of milling interventions and allows an obstruction-free path to the produced fluids. An overview of acid-resistant dissolvable frac balls deployed in a multi-lateral offshore multi-stage stimulation (MSS) application in conjunction with acoustic sensors is presented in this paper. A tri-lateral offshore well was drilled and completed with stimulation sleeve completions to perform multi-stage acid stimulation. The lower completion consisting of open-hole swellable packers and stimulation sleeves was successfully deployed with a metal-to-metal seal expandable liner hanger. The stimulation sleeves were successfully shifted open by the dissolvable frac balls. An additional real-time confirmation of the stimulation sleeve opening event was recorded with an acoustic system for every acid stimulation stage. Acoustic sensors provide increased operational efficiency through real-time diagnostic of dissolvable frac balls as they reach their respective baffles. Prior to deployment, the dissolvable frac balls were tested in a laboratory at downhole conditions to ensure that self-dissolution requirements of the frac balls are fulfilled. The dissolvable frac balls were successfully deployed in the offshore tri-lateral well, achieving required zonal isolation and hydraulic pressure integrity during multi-stage acid stimulation. Acoustic sensors provided real-time detection of each stimulation sleeve shifting open once the dissolvable balls reached their respective baffles. After the successful acid stimulation treatments, the frac balls dissolved from downhole conditions alone, allowing the return of full well-bore access on the three laterals for production. The utilization of dissolvable frac balls eliminated the subsequent coiled tubing milling interventions required with conventional frac balls after the stimulation. Significant costs and rig time was saved with this technology optimizing the post-stimulation phase of this tri-lateral well while achieving complete stimulation objectives. The dissolvable frac balls have proven to be acid-resistant in nature, with a differential pressure rating of up to 8,000 psi and temperature rating of up to 300ยฐF. The paper presents the successful application of an acid-resistant dissolvable frac ball deployed in a challenging offshore environment. The dissolvable frac ball technology proved to be successful under these challenging environments, saving significant time and intervention costs. Additionally, the application of an acoustic sensors is also discussed, which allowed efficient completion design and seamless execution.
Efficient Methodology for Stimulation Candidate Selection and Well Workover Optimization
Ugbenyen, Benson Oghenovo (African University of Science & Technology, Abuja, Nigeria) | Ogbe, David O. (African University of Science & Technology, Abuja, Nigeria) | Osisanya, Samuel O. (African University of Science & Technology, Abuja, Nigeria)
Abstract Nigeria is endowed with huge proven gas reserves estimated to be 184 trillion cubic feet (Tcf). It ranks as the seventh holder of natural gas reserves in the world, and the largest in Africa. Nigeria also flares more natural gas than any other country; it accounts for 12.5% of the world's annual gas flared equivalent to $2.0 billion of annual revenue wasted. There is crucial need, therefore, to reduce gas flaring and its environmental impacts, and to derive maximum economic benefits from gas production. Well stimulation consists of several methods used for enhancing the natural producing ability of the reservoir when production rate declines. The purpose of the study is to present a methodology and models for the selection, design and optimization of well stimulation. Production decline curve analysis is combined with economic discounting concepts to develop a model that can be used for optimizing stimulation decisions. The model is presented in the form of a non-linear programming problem subject to the constraints imposed by the production facilities, reservoir productivity and the stimulation budget approved by management. Production data from four stimulation candidate wells, offshore Niger Delta was used to validate the model developed by setting up a maximization problem. Solution to the problem was obtained using non-linear optimization software. The results show that the optimization model can be combined with stimulation treatment modules, developed from industry wide models, to quantify stimulation benefits. Candidate wells were then ranked based on stimulation cost, payout time and stimulation benefit. Proposed methodology and models can be used for stimulation candidate selection, ranking workover programs in a field and in optimizing stimulation decisions.
- Africa > Nigeria (1.00)
- North America > United States > Texas (0.68)
Abstract For nearly every producing field worldwide, acid stimulation is a type of intervention that is critical to longevity in production (or injection) for those wells. However, compared to other completions/intervention operations (e.g., cementing and hydraulic fracturing), several deficiencies have been identified in the historical training curriculum for acid stimulation. Legacy acid stimulation training is largely focused on the basic aspects of matrix stimulation, excluding many practical and contemporary topics. The current work details the development of an innovative, operations-focused training program for acid stimulation intended to augment historical training. To commission the development of new stimulation training curriculum, stakeholders from operations, management, and the technical function (subject matter experts) brainstormed the most critical needs for practical training that would add value to operations beyond current internal/external training material. From this, customized training material was built that includes new focus areas including a) : workflows were developed to prioritize likely types of damage that cause productivity/injectivity decline based on existing well data. These workflows led to further training regarding damage-focused stimulation design (rather than pure matrix/mineralogy-based design), to optimize stimulation/fluid selection to target specific damage in mature producers. b) : this includes customized training material related to stimulation of existing sand control completions, infant wells (unproduced), and laminated carbonate/sandstone pay zones. c) : this new training material addressed operational best practices including topics on specialized placement methods; on-site QA; and interpretation of pressure data (during stimulation). d) : the last aspect of the new training material includes students designing acid stimulation treatments for real candidate wells. The new operations-focused training material was piloted with several operations teams in 1-week intensive sessions, following the first week of (existing) basic acid stimulation training. This training (deployed both in-person and remotely) was well received by both the operations management and the students, who noted the enhanced relevance of the new curriculum to the production enhancement plans for the wells for which they are responsible. Additionally, the interactive team-activities to design stimulation programs for challenging wells (challenging mineralogy and existing sand control completions, multiple damage mechanisms, and wellbore mechanical obstructions) helped to improve acidizing designs for actual candidate wells through feedback from other students and class mentors. This work highlights the development and implementation of new training curriculum for acid stimulation design and execution, developed to improve the practical skills of production engineers and operations teams that design acid stimulation operations. Deployment of this new curriculum will help to improve the probability of success in acidizing some of the most challenging well conditions.
- Europe (1.00)
- Asia > Middle East (1.00)
- Africa (1.00)
- North America > United States > Texas (0.68)
- Geology > Mineral (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.49)
- Africa > Angola > South Atlantic Ocean > Lower Congo Basin > Area B > Block 0 > Greater Vanza Longui Area (GVLA) Field > Pinda Formation (0.98)
- North America > United States > Texas > Fort Worth Basin > Allen Field (0.93)
Effective Stimulation of Very Thick, Layered Carbonate Reservoirs Without the Use of Mechanical Isolation
Shuchart, Chris E. (ExxonMobil Upstream Research Co.) | Jackson, Shalawn (ExxonMobil Upstream Research Co.) | Mendez-Santiago, Janette (ExxonMobil) | Choi, Nancy Hyangsil (ExxonMobil Upstream Research Co.) | Montgomery, John K. (ExxonMobil Upstream Research Co.) | Khemakhem, A.S. David (RasGas Company Limited) | Sieben, Christopher John (RasGas) | Clancey, Byron Michael (RasGas Company Ltd) | Chintaluri S, Ram (RasGas Co. Ltd.) | Farah, Ali M. (ExxonMobil) | Wang, Zhihua (ExxonMobil Qatar)
Abstract Effective matrix acid stimulation is one of the keys to maximizing and maintaining long-term North Field well productivity. ExxonMobil and RasGas Company Limited (RasGas) had jointly developed an integrated methodology to optimize matrix stimulation for layered Khuff reservoirs, specifically for K1-K3 and K4 completions. The integrated methodology is a continuous process which consists of five main elements to help overcome the well and reservoir challenges, including reservoir objectives, completion strategy, stimulation design, implementation, and evaluation.1 Success of K1-K3 and K4 completions led to high expectations for K1-K4 completions required for the recent development expansion. However, the much longer K1-K4 producing interval substantially increased the challenges such that existing stimulation tools and methods were no longer sufficient to achieve the aggressive stimulation targets desired for these wells. Initially, retrievable mechanical isolation plugs were developed and qualified for use to achieve effective stimulation using already proven methods for K4 completions and K1-K3 completions. Due to the increased operational risk associated with mechanical isolation techniques, development of alternative methods and extension of existing methods were necessary. Multiple parallel paths were taken to investigate all aspects of well stimulation, including perforating techniques, diversion, number of stimulation treatments, stimulation vessel capabilities, and well / reservoir productivity. Field trials were conducted for selected technologies, and additional data were collected prior to, during, and after the stimulation treatments. Additionally, a process and associated tools to quantitatively evaluate completion and stimulation options in terms of both initial and long-term production performance were developed. Consequently, stimulation decisions could be made based on reservoir performance metrics balanced with the risks and costs associated with each option. To evaluate well performance and optimize the stimulation strategy for future wells, an advanced post-stimulation analysis methodology incorporating stimulation predictions, sequential flow data, flowback samples, and production logs has been developed. Results of the analyses suggest stimulation performance comparable to stimulation with plugs, at a greatly reduced completion cost and substantial risk reduction and time savings. Additionally, stimulation strategy optimizations were possible such that the number of stimulation treatments could be reduced for most wells without compromising stimulation effectiveness or predicted long-term performance. This paper discusses the development and implementation of alternative strategies and designs to effectively stimulate K1-K4 completions without the risk associated with mechanical plugs. Two case histories will be presented to illustrate application of the enhanced methodology.
- Asia > Middle East > Qatar > Arabian Gulf (0.26)
- North America > United States > Texas > Dawson County (0.25)
- Asia > Middle East > Qatar > Arabian Gulf > Rub' al Khali Basin > North Field > Laffan Formation (0.99)
- Asia > Middle East > Qatar > Block 4 > Khuff Field > Khuff Formation (0.98)
Abstract Carbonate rocks constitute a significant portion of hydrocarbon reservoirs worldwide. Due to their unique geological deposition, carbonate formations have different ranges of heterogeneities such as mineralogies, permeabilities, fluid properties, fissures, natural fractures, and reservoir pressures. On top of their inherent heterogeneities, well operation activities such as drilling and well intervention can damage the formation. In the lower-permeability formations, a maximum reservoir contact (MRC) well is a preferred option to extract hydrocarbon from the reservoir. An MRC well involves specific challenges from the well completion perspective that eventually could impact the productivity. Carbonate stimulation is a long-standing technique to increase productivity in carbonate formations. Stimulation treatment in general improves the hydrocarbon deliverability to the wellbore and eventually to surface. It also removes or, on some occasions, bypasses the damage in the wellbore. With a long horizontal well, more surface area must be stimulated; however, more surface area means there is more heterogeneity to overcome as well. This paper describes the importance of acid stimulation planning as well as modeling, which plays a vital role in effectiveness of acid stimulation job in horizontal wells with different MRC completion types and achieving the best results of productivity enhancement in carbonate fields. Log-and-completion-based simulation software was used to model the formation heterogeneity in combination with well completion complexity. Different modeling scenarios based on well trajectory and completion design are simulated together with the reservoir heterogeneity such as different permeability, possible fissures, different reservoir pressures. Different acid systems are also simulated against these heterogeneities and complexities. The stimulation modeling results show that stimulation uncertainties arise when both completion complexity and reservoir heterogeneity are present. A stimulation integrated workflow following the stimulation design workflow in the latest log-and-completion-based software is presented. Some case studies in UAE related to these challenges are presented with some key lessons learned. Some advanced carbonate acidizing technologies are implied in this observation to achieve the stimulation objectives.
- North America > United States > Texas (0.28)
- Asia > Middle East > UAE > Abu Dhabi Emirate > Abu Dhabi (0.15)
- Geology > Geological Subdiscipline (0.86)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock (0.34)