Production Enhancement & Cost Effective of Deep Gas Wells by Using Cluster Perforation Technique of Carbonate Reservoirs in Kuwait: Case Studies

Abstract

Abstract North Kuwait Jurassic Gas (NKJG) fields are challenging HPHT wells with near-critical fluids in reservoir conditions. These wells are deep and sour with 2-8 % H2S and 1-3 % CO2 with average reservoir pressure ranging from 10,000 – 4,000 psi and average reservoir temperature of ~275oF. Best practices in terms of developing these fields by using the best technologies in drilling, completion, and production are essential to maximize the reserve recovery in order to deliver hydrocarbon to the market. Due to anhydrite presence and existing high variation of natural fracture distribution along the wellbore with different lithology and reservoir properties. There is differential pressure depletion happens within the entire reservoir, so these reservoirs have been divided into different flow units based on stratigraphy and pressure differential. These layers have different productivity index based on production logging records and calibrated well production models due to existence of dual-porosity tight matrix with natural fracture system which require proper pinpoint activation protocol by treating these layers separately. During the early development stages of these fields, these wells were completed with tapered type of completion with 3.5″ production tubing, which was used as the optimum flow rate for virgin or slightly depleted reservoirs. Nowadays, Monobore completion has been deployed so that these flow zones can be perforated, activated, stimulated, tested and isolated using plug and perf technique which provide proper stimulation fluids propagation into the target reservoir. In addition, the cluster perforation leads to better effective stimulation fracturing by bypassing formation damage due to drilling, completion & perforation debris from the illustrated case studies. This paper aims to illustrate the successful story of the cluster perforation technique in tight carbonate reservoir layers, and share its impact on pinpoint stimulation and hydraulic fracturing treatment by comparing the production performance of the studied wells with offset wells. As an additional achievement, the cluster perforation leads to cost reduction by reducing the perforation gun length, volumes of pumped treatment/wellbore diverters fluids and accelerating the well hookup to the production facility beside the sustainability of the production during the LTT. Also, that technique is better in terms of reservoir management as it supports depleting the reservoir layers uniformly. The success of this approach was proven by calibrated nodal analysis assessment and sustainability of well production at a stabilized rate, which supports reaching "optimal inflow distribution" along the different flow zones, which become a best practice approach in the newly completed wells aiming to maximize the gas recovery.