Frac-hit characteristics and productivity maintenance strategies of deep shale gas wells:A case study of northern Lu 203 well block in the Sichuan Basin
Frac-hit characteristics and productivity maintenance strategies of deep shale gas wells:A case study of northern Lu 203 well block in the Sichuan Basin
Exploration and development of shale gas reservoirs in China has stepped into a new stage of industrialization and large-scale production.With the increasing number of shale gas platform wells and the increasing scale of fracturing operation by shale-gas horizontal well,it is a common problem that fracturing fluid flows into old wells during the fracturing of new wells.The highly developed natural fractures in the Longmaxi Formation shale reservoir make the frequency of frac-hit in the Luzhou Block of the Sichuan Basin significantly higher than that in the common shale gas blocks.The frac-hit problem of shale-gas horizontal well has a serious restriction to the large-scale benefit development of deep shale gas in this block.In order to effectively treat the frac-hit of shale-gas wells in the Luzhou block,this paper summarizes the frac-hit characteristics of shale gas wells in Lu 203 well block,and establishes material balance equation and fracturing fluid encroachment calculating method considering frac-hit.Based on this,a series of field experiments of fluid drainage and productivity maintenance of frac-hit wells are carried out.And the following research results are obtained.First,Lu 203 well block exhibits three major characteristics,i.e.,complex frac-hit distance,complex frac-hit path,and complex pressure change.Second,the fracturing fluid encroachment can reflect the severity of the frac-hit.The greater the fracturing fluid encroachment is,the more difficult it is to restore the production of a shale gas well.Third,the regional overall fluid drainage and production restoration strategy called"encircle and eliminate;fluid drainage near fracturing wells,and gas production far away from fracturing wells"is put forward,and its field application effect is remarkable,with the regional gas production after the production restoration increasing to the level before the frac-hit.In conclusion,the established fracturing fluid encroachment calculating method and the overall fluid drainage and production restoration countermeasures can provide a guidance for the effective treatment of frac-hit in deep shale gas wells,as well as a reference for the productivity maintenance of the similar shale gas reservoirs.
关键词
四川盆地泸州地区/龙马溪组/深层页岩气/压窜/物质平衡/侵入压裂液量/产能维护/排液复产
Key words
Luzhou area of the Sichuan Basin/Longmaxi Formation/Deep shale gas/Frac-hit/Material balance/Fracturing fluid encroachment/Productivity maintenance/Fluid drainage and production restoration
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