Long Horizontal Slim-Hole Cementing Technologies for Cost-Effective Development in a Middle East Ultra Low Permeability Reservoir

Abstract The Sadi ultra-low permeability reservoir accounts for more than 25% geological reserves of a giant Middle East Oilfield. 70 horizontal wells with more than 5000m MD have been planned and the infinite stage cementing fracturing technique are proposed in 1000m-2000m horizontal section for Sadi reservoir cost-effective development. The liner cementing quality in long horizontal section is the key to the success of good zonal isolation and premises of effective hydraulic fracture operation. To improve the efficiency and performance of 4 1/2″ liner cementing, a comprehensive series of numerical simulation of cementing process and experimental research of core additives have been carried out to overcome slim-hole cementing challenges such as poor centralization, insufficient mud removal or displacement, and low cement bond quality. The cementing operation procedure was optimized including centralizer selection, cementing liquid volume design, Rheological property design and cementing operation parameters. The integrity mechanical model of cement sheath was established so that to design the high efficiency washing space fluid and flexible cement slurry based on experimental results. By simulating mud removal and cement slurry placement process, integral elastic centralizer and centralization program was recommended, sequence of cementing fluid with appropriate density and volume was determined. the rheology property of Spacers/ Lead slurry / tail slurry was determined in view of the friction resistance hierarchy concept, and variable pumping procedure has been optimized to achieve better effective mud displacement. Meantime, the mechanical properties of the cement sheath was demonstrated by integrity analysis under the condition of multistage fracturing in horizontal section, and concluded that cement sheath shall meet the requirements of Elastic modulus 6.5GPa, Poisson’s ratio 0.18, Compressive strength 24MPa, Tensile strength 2MPa. In terms of cementing fluid. A new toughening agent was also developed to improve the mechanical property of cement sheath to meet the requirements of infinite stage cementing fracturing operation. Liner cementing key techniques has been developed to achieve effective zonal isolation and good cement bond quality in challenging long horizontal slim-hole cementing and application in-site horizontal well cementing job and achieved the good cement bond quality, this technology is expected to deliver a successfully optimized liner cementing operation for future horizontal wells cementing.