Chongqing Gas Field Gas Field Produced Water Re-injection Feasibility Study

With the demand of natural gas increasing, the production has been increasing annually. So more gas field water has been recovered. For reducing the cost and protecting the environment, usually the gas field water has been reinjected into reservoirs.Based on the analysis of current situation of reinjection wells in Chongqing Gas Field, reinjection effect and impact mechanism on reservoir seepage physical property caused by reinjection water quality and the study of reinjection ability of reinjection reservoir, here are the main understandings: Most gas reservoirs in Chongqing Gas District belong to low permeability or extremely low permeability carbonate reservoirs, others belong to sand rock reservoirs which are in Jurassic system and Xujiahe group in upper Triassic. Therefore, when selecting reinjection reservoir, it is important to prevent choosing those low permeability reservoirs. The laboratory study of compatibility between reinjection water quality and reservoir indicates that the compatibility of reinjection water and formation water is pretty good; And the result of core sensitivity evaluation of well Chi 63, Jia II~2 indicates that the reservoir is weak velocity sensitive and strong water sensitive. Those are not proper for being the reinjection reservoir. Presenting the field water reinjection general principle: If it can inject without any surface leakage. And trying to simplify field water treating process mainly through controlling aqueous suspension content and petroleum content in the reinjection water. Presenting reinjection well selection principle: Using exhausted well with high recovery ratio, enough effective porosity and sound permeability as reinjection well, or drilling a new reinjection well. Presenting reinjection reservoir selection principle: narrowed buried with good sealing; enough accumulation space, good permeability and water absorption; good isolation between lower and upper seal coats, good horizontal communication in injection zones, no surface water leakage, seal coat will not fracture to cause injection water go to other zones under high pressure; good compatibility among injection water, reinjection reservoir rock and formation water, not high formation pressure, energy loss, the less pressure the better at wellhead ,the best self-absorption injection; trying best to locate the injection well near the production well to reduce pipeline transmission distance and cutting down cost. Establishing the study method of reinjection ability and study on the reinjection ability impact factors.This study presents a set of idea and method for produced water reinjection study.