Sanding in Response to Dynamic Changes in Downhole Conditions

Abstract Downhole conditions from the sanding risk viewpoint refer to anything in the downhole that affects rock disaggregation and sandface fluid flux, two principal factors dictating well’s sanding response. Often times similar wellhead flow rate and pressure may be associated with drastically different downhole conditions and their dynamic changes, resulting in complex and counter-intuitive sanding responses. Due to their practical significance but difficulties in reliably predicting all of them in advance, this paper describes a sanding-physics-based data integration approach to get them consistently identified for the practical purpose of taking the right course of action to safely maximize well’s flow potential, and prevent, mitigate and manage well-specific sanding issues. It requires a multi-disciplinary effort and cross-referencing well production histories fieldwide is an integral part. Equally important are the prior sanding-mechanisms-based empirical relations between sanding severity and driving factors, refined reservoir engineering simulation, and numerical sanding prediction that considers effects of rock disaggregation, depletion, drawdown, fluid flux and water in one-go. Three field cases are presented to illustrate the approach. Each case is distinctively different although they all involve cased & perforated (C&P) high-rate gas wells in competent formations that have been online for years but without formation water breakthrough yet. In Case-1 uniform reservoir pressure distributions between reservoir formation subunits and production logging tool (PLT) surveys in each well have provided a reliable delineation of gas flux distributions and shut-in induced temporary wellbore water buildups. That has led to a consistent understanding of well specific sanding in relation to high gas flux and water buildups at a low rock disaggregation state. In Case-2 differential reservoir pressures /depletions in different units of a multi-stacked reservoir pay system under a commingled production have resulted in dynamic changes in drawdown, gas flux and downhole water activities, and thus complex sanding responses including prolonged perforation debris cleanout, high drawdown induced sanding and water-crossflow induced sanding during post shut-in production ramping. In Case-3 a thorough review of limited data available in 4 wells has inferred that the interaction between smectite-bearing formation intervals and temporary wellbore water buildups and its limited near-wellbore damage and subsequent self-cleanup under drawdown and gas flux are responsible for observed well-specific cyclic changes in drawdown and minor sand events prior to depletion induced rock disaggregation. Despite observed sand production in all 3 fields neither permanent production chokeback nor intervention are needed to date. Rather, well specific sand management strategies and surveillance tailored toward tendencies of well-specific dynamic changes in downhole conditions have been implemented to safely achieve the targeted gas rate.