ABSTRACT:

Geomechanical sanding evaluation has become a key tool in the development of fit-for-purpose sand management strategies and well completion decisions for the reservoir and well life cycle. Geomechanical analyses can identify the likely sand producing intervals, the timing (pressure conditions) and the severity of sanding. Sanding evaluations are ideally calibrated against field sanding observations or rock mechanical simulations of laboratory tests on representative rock samples. However, in the absence of field observations, the validity and credibility of geomechanical analyses can be a concern for field development planning, well design or well intervention decision. This paper focus on the credibility of geomechanical sanding risk evaluation, conducted at appraisal and early field life stages, for sand control and completion decisions. It includes five field studies from the Asia Pacific region with a range of geological settings, stress regimes and rock strengths, well types and operation conditions. The case studies include; 1) deviated sand-prone gas wells with no downhole sand control, 2) horizontal sand-free gas wells, 3) deep-water oil wells under high water cuts and moderate depletions and drawdowns initially sand-free with sanding incidence later, 4) and 5) two shallow water oil fields with high angle and horizontal wells both operating under water-cuts but still sand-free after many years of production and high pressure depletions. The case studies demonstrate the validity of geomechanical assessments conducted at early field life that are verified with several years of production later, each with different outcomes and observations. It is concluded that with robust geomechanical modelling and frequent updates, reliable sanding risk assessments can be provided to well engineers and asset managers for fit-for-purpose and timely sand management and completion decisions.

1. Introduction

Sanding or solids production could have multiple adverse effects on the productivity and integrity of wells and also is a potential health, safety and environmental hazard. The presence of sand gains in produced fluids often results from mechanical failure of formation rocks under drawdown conditions. Such rock failure condition is not uncommon in mechanically weak rocks, with high in-situ stresses or in high depletion conditions, with or without water production. The occurrence of sanding in wells depends on the field geomechanical parameters, well operations and reservoir management and performance. Sanding needs to be managed to ensure safe operation, maximum productivity and hydrocarbon recovery. Effective sand management and the optimum solution to either delay, exclude, or co-produce the sand to surface, requires an understanding of the mechanisms that cause sanding and the development of a field- and often reservoir-specific model to define the critical pressure conditions for sand production. The optimum sand control and completion decision is then selected based on the field development plan, production forecasts, reservoir rock characteristics, facilities considerations, well type and completion design, legislation, and environmental considerations.

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