Conductivity Enhancement and Productivity Restoration of Deep North Kuwait Jurassic Gas-Condensate Well by Using Effective HRMA Stimulation Technique

Abstract

Abstract Achieving sustainable gas and condensate production from carbonaceous North Kuwait Jurassic Gas (NKJG) reservoirs has been challenging due to multi-dimensional inflow/outflow complications under restrictive operating downhole conditions. Production from the NKJG reservoirs has strategic importance for the State of Kuwait, where the formations are deep and sour, and produce gas-condensate and volatile oil, in which the produced fluids contain from 2 to 8% H2S and 1 to 3% CO2. High reservoir pressure of up to 12,000 psi is widespread trapped below an over-pressured salt structure. NKJG reservoirs have high temperature of ~275°F and have been recently completed with monobore completions, to optimize overall commingled well performance and to ensure operational optimization of future well interventions. Differential depletion has had significant consequences in well and reservoir management including the design and execution of stimulation treatments, particularly the "high rate matrix acidizing (HRMA)" applications. In addition, vertical variations in lithological and mechanical rock properties contribute to drilling challenges which are progressively exacerbated as the deepest zones continue to produce most of the hydrocarbons whereas other potential horizons are not exploited at similar rates. Monobore completions have been deployed so that each flow unit could be segregated and stimulated separately, starting from the bottom, moving uphole as each stage is treated, activated, tested and isolated using drillable bridge plugs. After all zones are completed, the bridge plugs are drilled out using coiled tubing mills and commingled production is established from all zones. To overcome this complex technical challenge while utilizing the funds and resources efficiently, the team in charge of the project developed a novel method of assessing the zones similar in reservoir characteristics and generated a "bullheaded HRMA treatment design" concept which was applied in the subject well while stretching the length of the perforation interval to a gross 216 ft that can be effectively covered with sound wellbore diversion methodology using particulate chemical diverters as well as leak-off control diverters. The custom-designed fluid train was tailored to effectively stimulate each conductivity unit, followed by diversion into the subsequent stages. The perforated interval length has been stretched to 285 ft in subsequent wells based on the success of this well. The completion and intervention history of the subject well is covered in this paper followed by the successful field implementation of the HRMA application as a case study, and to share the learnings and recommendations providing pre-stimulation and post-stimulation production logging comparisons. As an additional challenge, the HRMA treatment overcame the heavy near-wellbore damage created during a workover fishing operation due to the well-kill with heavy drilling fluid. The results are confirmed by calibrated nodal analysis assessment providing evidence of the success in deploying this technology in unconventional tight gas reservoir of less than 10 mD permeability. Achieving optimal inflow distribution along vertically varied flow zones has enabled the asset to deploy this systematic approach in other new wells in the NKJG while saving significant cost and time.