致密砂岩气藏水平井全通径分段压裂改造实践及认识

PRACTICE OF FULL BORE STAGED FRACTURING STIMULATION FOR HORIZONTAL WELLS IN TIGHT SANDSTONE GAS RESERVOIRS AND KNOWLEDGE OBTAINED

鄂尔多斯盆地北部致密砂岩气藏开发前期,形成了以裸眼预置管柱管外封隔分段压裂为主的水平井改造模式,为气田快速有效建产提供了技术支撑.但在后期生产实践中,该技术逐渐暴露出多级滑套内径逐级递减,不能实现压后井筒全通径;憋压球不能全部返出,部分滞留井筒而影响后期二次改造等问题.针对这些问题,逐步开展了基于套管固井完井和裸眼封隔器完井的全通径分段压裂试验.实践表明,基于套管固井完井的全通径改造模式压后效果不理想,还需要进一步加强研究攻关.基于裸眼封隔器全通径完井及连续油管带底封分段压裂的改造模式,既具有裸眼完井泄气面积大,“甜点”自选等优点,又具有套管固井完井压后全通径的优点,利于后期排液采气和二次作业.通过不断完善配套技术,该工艺逐步趋于成熟,施工成功率达到98.6%,初步形成了适用于鄂尔多斯盆地北部致密砂岩气藏的水平井全通径改造模式,具有较好的推广应用价值.

During the early stage of tight sandstone gas reservoir development in Northern Ordos Basin,the staged fracturing with preset pipe string and packer in open holes is the main stimulation model for horizontal wells,which provides technical support for the rapid and effective production of gas field.But in the later production stage,the inner diameter of multi-stage sliding sleeve gradually reduce stage by stage,full bore after fracturing cannot be achieved.Pressure balls cannot be all returned,some ones remaining in the wellbore will affect the latter secondary stimulation.In order to solve these problems,full bore staged fracturing tests based on casing cementing completion and open hole packer completion are carried out step by step.The effects of full bore staged fracturing based on casing cementing completion is not satisfactory,further research is needed.The open hole packer completion combined with staged fracturing by coiled tubing with bottom packer has the advantages of large drainage area and automatic"sweet spot"location in open hole completion,it also has the advantages of full bore formed after casing cementing completion,which is beneficial to gas production by water drainage during secondary stimulation.Through the continuous improvement of matching techniques,this technology has become more mature,and the success rate of operation has reached 98.6%.It provides a good model of full bore staged fracturing for horizontal wells in tight sandstone gas reservoirs at northern Ordos Basin,and has valuable prospect for application.