Multi-modal Particle Size Distribution of Lost Circulation Material Blend forControlling Fluid Losses from Multiple Fractures Around Inclined Wellbores

摘要

Lost circulation material (LCM) is commonly used to stabilize formations and inhibit fluid losses from thewellbore during drilling. Mud loss records and wellbore downhole image logs often reveal existence ofmultiple natural and drilling-induced fractures in the wellbore vicinity. Appropriate particle size distribution(PSD) for the LCM blend should be designed so that lost circulation from all near-wellbore fractures iscontained. This paper presents a novel design scheme for multi-modal PSD of LCM blends applicable to the likelycases of lost circulation from multiple near-wellbore fractures. The design scheme takes advantage of ananalytical solution which estimates the fracture widths of an arbitrary number of fractures around inclinedwellbores when subjected to the three principal stresses of the subsurface. The LCM blend design involvesdividing the blend into subcategories of various sub-blends sizes. Each sub-blend has distinct particlesize distribution, when combined, satisfying the size distribution criteria on the quantile distribution basis.The fractures apertures widths, which are a crucial input for LCM blend selection, are determined froman analytical solution of the related wellbore geomechanics problem. The solution is derived from thedislocation-based formulation of fracture opening profile in an infinite poroelastic medium. The effectsof overburden stress, anisotropic horizontal stresses, wellbore inclination and azimuth as well as themechanical interaction between the cracks are incorporated in the analysis. Further, a systematic method tocharacterize mud cake parameter is employed. Mud cake efficiency is shown to cause considerable influenceon fractures aperture width and consequent composition of the LCM blend.