Sand Management Solutions for High-Rate Gas Wells, Sawan Field, Pakistan

摘要

Formation damage, sand production and a HP/HT sour gasenvironment are major challenges in the field development ofthe Sawan gas reservoir in Pakistan. Meeting individual wellproductivity targets (average of 80 MMscfd) requiresminimal-restriction (large bore or monobore) completions,minimizing formation damage via under-balance perforationand maintaining sand production below tolerable limits.The reservoir sands are extremely heterogeneous withmany thin, weak layers. Sand control completion concepts arebased either on internal gravel packs (IGP) or, if the weakerlayers are less extensive, on selective perforation. To avoidhaving to kill the wells (which can lead to significantformation damage) the completions are run prior toperforating. This meant that the sand control decision for eachdevelopment well had to be made in 3 to 4 days - betweenlogging the well at TD and running the completion.The key elements of this “real time” sand managementstrategy were:? the application of Fuzzy Logic computing techniques tocorrelate wireline log responses with core measurements,which enabled a field-calibrated, continuous sand failureprediction tool throughout the reservoir intervals;? coupled well performance and geomechanical models toevaluate if selective perforation could safeguard welldeliverability yet ensure sand-free production,standardization of critical completion equipment andsimplified nipple-less completion design which providedthe necessary operational flexibility, lowered overallcompletion cost, and reduced the risk ofequipment failure.? under-balanced through-tubing perforation with coiledtubing to minimize formation damage.This integrated completion and sand management strategyhas delivered well production rates in excess of 100 MMscfdwith sand production significantly below tolerable limits. Ithas also has created substantial cost savings and reducedcompletion failure risks compared to conventional cased-holesand exclusion completions.