North Kuwait Jurassic Gas Experience of Expanding Multistage Completion Strategy for Managing Deep Tight Gas Development Challenges

Abstract

North Kuwait Jurassic Gas asset has strategic importance for Kuwait production strategy as the only non-associated gas producing fields in Kuwait. This paper demonstrates the added value, experience, challenges and lessons learned of recent paradigm shift in Jurassic tight gas wells’ completion strategy from cemented liner to multistage completion. A successful expansion of Multi-Stage Completion (MSC) technology has been achieved on field level led by integrated team efforts since early 2020 to date. This helps to enhance overall well production potential, selective stimulation, overcome reservoir and intervention operations challenges, and early production delivery. The Jurassic gas asset produces mainly from deep high pressure and temperature, conventional and unconventional tight carbonate reservoirs. The recovery from such complex heterogeneous reservoirs is extremely challenging if conventional development strategies are applied. Due to the high reservoir tightness, permeability contrast among different flow units and dual permeability effect (matrix and natural fractures), well productivity potential significantly depends on the effectiveness of subsequent stimulation treatments of such complex heterogeneous reservoir to improve well productivity and connect the natural fractures. Selecting proper well completion is critical to overcome such reservoir challenges and ensure efficient acid stimulation treatments of such unconventional formations that need convenient diversion mechanism during the stimulation to enhance the productivity of each individual reservoir layer, and enable future flexibility of selective re-stimulation and reservoir management. The asset team has applied a step change in completion strategy to open-hole HPHT multistage drop-ball completions using state-of-the-art MSC technologies including closable frac ports, full 3.5in monobore post milling and debris sub to protect the MSC string during upper completion operations. This is to overcome such reservoir complexity, eliminate wellbore cleaning and multiple perforation intervention operations challenges and risks, eliminate cement quality uncertainties, improve overall cost, and fast track well delivery to production to meet asset production target by significantly reducing operation time from approximately one month of plug and perf technique to less than one week of continuous and less subsurface intervention operations. Total of 23 new Multi-stage completions were successfully installed in last 2 years including 4 systems in horizontal unconventional Najmah reservoir with overall good production results and significant improvement in selective acid stimulation (matrix and Fracturing), intervention operations efficiency and fast well delivery to production. Therefore, the asset plans to continue expansion in Multi-stage completion strategy. Based on gained experience, an integrated protocol for multi-stage candidate well selection, staging design and installation procedures workflow has been built by the integrated multidisciplinary team to ensure standard process across fields which can be used for application in other fields.