This paper demonstrates the production optimization methodology being used by Kuwait Oil Company Jurassic gas that added significant contribution of approximately 37% of total field incremental production gain in 2021. Production optimization is a continuous iterative process to improve production, especially in mature fields. The North Kuwait Jurassic Gas field’s team has adopted an integrated enhanced and structured process to identify opportunities for production optimization with a pro-active approach focusing on flowing wells and rig-less interventions to tackle production challenges and achieve production targets. The Jurassic gas asset has unique mature-field challenges. It produces mainly from deep (up to 19,000 ft MD) high pressure and temperature, conventional and unconventional tight carbonate reservoirs, highly deviated to horizontal wells, different completion configurations (4.5in monobore, 3.5in × 5in liner, and 4.5in Multi-stages completions), wellbore cleaning and accessibility, scaling and flow assurance, high heterogeneity and permeability contrast among different flow units and dual permeability effect (matrix and natural fractures), production decline due to pressure depletion, liquid loading, high H2S (up to 13 mol%), surface production facilities limitations (e.g. limited MP and H2S handling capacity). effectiveness of subsequent stimulation treatments of such complex heterogeneous reservoir to improve well productivity and connect the natural fractures. The recovery from such complex heterogeneous reservoirs is extremely challenging if conventional development strategies are applied and need for appropriate production optimization methodology outlined here. The Heterogeneity Index process is utilized to rapidly demonstrate production gain opportunities via quick screening method of identifying preliminary candidate wells with anomalous behavior (over/under performance) for further analysis. The results from this screening tool were utilized to identify the families of type productivity problems at field and well levels with solution categories for production enhancement. Representative wells were selected for detailed diagnostics based on the relevance and size of productivity impact and the potential of its well deliverability. Once a few "top potential" wells were identified, production engineering workflows were implemented to assess and forecast the potential of production increase and to determine and evaluate the best solution design and intervention action. Detailed production optimization process provided recommendations of various remedial intervention solutions to improve well production potential via productivity enhancement ranging from complex matrix and fracturing stimulation, additional and/or re-perforations, wellbore cleaning, flow assurance solutions, to choke management. Other advanced technologies were applied to improve various strategies, including completions, perforation, stimulation, and production control. The executions of recommended interventions added significant contribution of approximately 37% of total field incremental production gain in 2021. Such production optimization process, experience and lessons learned will be shared where it can be used in analog fields.
Producing hydrocarbons at appraisal and development targets from deep, sour, over-pressured and HPHT carbonates in North Kuwait has been a challenge driven by the complex reservoir heterogeneity as well as the damage induced by the use of barite-laden heavy oil-based mud (OBM) in drilling and during installation of production tubing as completion fluid. Due to the tight formation properties and the added damage induced by OBM, matrix acidizing does not always deliver hydrocarbons at economic rates. Such zones require hydraulic fracturing under challenging conditions imposed by the wellbore limitations, such as high degree of deviation, smaller tubing as the frac string, and length limitations of the seal-bore assembly, as well as the on-site presence of a deep drilling rig to complete the tests effectively and on-time. Tubing conveyed perforation (TCP) and wireline perforation techniques require wells to be subdued prior to the installation of final completion due to the over-pressured reservoir conditions and requirement to perforate with as large guns as possible. Both of these techniques have proven less then efficient as the flow tests performed before and after running final completion historically indicated significant drop in production of hydrocarbons. Therefore, a gun hanger shoot-and-drop perforation system was customized to facilitate underbalance perforation and immediate well clean up with no further well-kill requirement whilst still utilizing optimum gun size for better perforation geometry. As an added challenge, the requirement to hydraulically-frac the tight carbonates necessitated modeling and design of tubular movement, stress analysis & drag modeling in the highly deviated case described in this paper. Determining the operational pressure envelope to complete the hydraulic frac treatment safely and effectively (operations pressure management) was the critical success factor in the placement of large acid hydro-frac without jeopardizing the wellbore (PBR seal) integrity. Customized "surfaceadjusted" weight of tubing slack off methodology was developed and implemented, resulted in maintaining safe operational conditions during the hydro-frac where the wellhead treating pressures exceeded 13,000 psi. Because of the specific perforation technique and analytical approach required for optimal treatment pressure management, a complex data-frac program followed by a large and customized acid hydro-frac program were successfully implemented with the facilitative function of the deep drilling rig on the well site. Collection of critical completions data was achieved and the reservoir deliverability was established while wellbore integrity was maintained. Mechanical formation properties were determined and hydro-frac geometry on effectively connecting to the higher mobility segments of the reservoir was realized. This paper will also outline the future optimization plans based on the learnings from the frac tests conducted in the well.
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