Minimizing Sanding Risk by Optimizing Well and Perforation Trajectory Using an Integrated Geomechanical and Passive Sand-Control Approach

Abstract

Abstract The source of sand production is the presence of disintegrated sand grains due to rock failure at the wellbore and/or perforation walls. Decision for appropriate sand control strategy requires engineering analysis to evaluate timing and severity of sanding over the life of field conditions. Optimizing well parameters such as well trajectory, perforation orientation, and level of drawdown using geomechanical principles can minimize and delay sand production. This paper presents a geomechanical modeling approach that integrates production history with information from drilling data, well logs and rock mechanics tests. A gas field in South Asia with 11 wells and several years of production experience is used to demonstrate this approach. Core-calibrated rock strength log profiles are estimated throughout the reservoir depth for all existing wells. A rock failure criterion at the sand face is developed as a function of in-situ stresses, rock strength, well trajectory, perforation orientation, reservoir depletion and drawdown. Sanding evaluation results are calibrated and verified with production data and evidence of sanding in existing wells. Sand-free operating envelopes and sand evaluation logs are then generated for all existing wells and planned infill wells for life of field conditions. Sand prone zones and timing of sanding are established as a function of depletion and drawdown for each well using production forecasts for the rest of field life. For new infill wells, optimum well trajectories, selective perforation intervals and optimum perforation orientations are proposed to minimize and delay sand production. Re-completion and utilizing passive sand control methods including selective and orientated perforations are recommended for a number of existing wells. This paper is expected to provide well engineers with guidelines to understand the principles and overall workflow involved in sand production prediction and minimization of sand production risk by optimizing well trajectory, perforation orientation and selective perforation strategy. Introduction Mitigation of sand production is increasingly becoming an important and challenging issue in the petroleum industry as ever increasing demands for oil and gas resources are forcing the industry to expand its exploration and production operations in more challenging unconsolidated reservoir rocks and depleted sandstones with more complex well completion architecture. A sand production prediction study is now an integral part of an overall field development planning study to see whether and when sand production will be an issue over the life of the field and, depending on its timing and severity, what type of sand control measures and sand management strategy will be cost-effective for the field. The source for sand production is the presence of disintegrated sand grains around the wellbore or perforation walls. The source for disintegrated sand grains may be the unconsolidated reservoir sands or rock failure around the borehole or the perforation. While unconsolidated reservoir sands often call for sand control measures from the beginning of the production phase, the sand production prediction study provides much benefit for reservoirs having sandstones of weak to intermediate strengths. Rock failure in such reservoirs may be minimized by controlling the well trajectory, perforation orientation, perforation intervals and drawdown by knowing the in-situ stresses and rock strength in the field. While standard methods are available for in-situ stress and rock strength characterization, the solution over the field life becomes complex due to the change of reservoir pressure and its effect on rock failure.