Proppant Fracturing for Creating Conductive Dendritic Fractures in Repeatedly Acid Stimulated Limestone Water Injection Wells of Indian Offshore:Traditional vs Complex Fracturing Technique

摘要

Limestone reservoirs of Mumbai High field are multilayered,heterogeneous formations having low to moderate permeability. Water injection wells in this field are normally stimulated using different acidization techniques which gave good results but sustainability was the problem.Proppant fracturing in limestone reservoirs is subjected to various challenges like excessive fluid loss,presence of natural fractures,cavities/vugs created by earlier stimulation treatments etc.This paper describes the proppant fracturing jobs carried out in already acid stimulated water injection wells of Mumbai High limestone reservoirs of Indian Offshore both in conventional manner and complex fracturing based on reverse flow stimulation technique. Fracturing fluid developed,optimized for creating complex fractures and prop open with proppant in these limestone reservoirs.Complex networking fracture technique applied in limestone injector which aimed for more no.of conductive dendritic channels rather than single large channel in the conventional fracturing technique.In this fracturing technique proppant rates and pumping rates will be varied during the job so that more no.of channels can be created,filled with proppant and connect to natural fractures.Proppant fracturing jobs were carried out in two nos.of water injection wells(AA and BB) which were earlier acid stimulated for a no.of times. Proppant fracturing in the well AA is executed in conventional manner where 30MT of 20/40 proppant pumped and fracturing in the well BB is executed to create more conductive dendritic fractures using reverse flow stimulation technique where a total 48.48MT of 20/40 proppant pumped in two stages.Post proppant fracturing,the injection rate increase in the well AA is moderate,whereas in the well BB,the injection rate got almost doubled.This paper discusses in detail the challenges, operational aspects,laboratory studies,design considerations and execution methodology of proppant fracturing campaigns carried out in water injectors of Indian limestone reservoirs. This complex fracturing technique is very much useful for creating more no.of conductive dendritic fractures.This technique can be applied to repeatedly stimulated limestone reservoirs.Wherever traditional proppant fracturing technique is not giving the desired results,this technique may be tried so as to improve post frac gains.