玛湖致密砾岩油藏水平井体积压裂技术适应性分析

Adaptability of horizontal well volume fracturing to tight conglomerate reservoirs in Mahu oilfield

细分切割体积压裂技术已在玛湖11个致密砾岩油藏应用118井次,验证了工艺的针对性和可操作性,压裂工程参数指标不断取得突破,水平井生产效果显著提升,但合理压裂工程参数与最优生产效果间的匹配关系仍不确定。为了优选合理的工程技术参数范围以指导后续水平井压裂设计,也为了提高致密砾岩油藏开发综合效益,开展体积压裂技术适应性研究。通过数据统计和趋势预测等分析手段,将水平井压后产量、压力等生产数据与体积压裂方式、完井压裂工艺、裂缝参数、压裂规模、压裂材料选型等压裂工程参数相对应开展分析。研究表明,针对物性较差的常压油藏,合理的压裂裂缝间距为25~35m,合理改造规模为加砂强度1.2~1.5m^3/m、砂液比(1:17)^(1:20);针对物性较好的异常高压油藏,合理的压裂裂缝间距为40m左右,合理改造规模为加砂强度1.0~1.2m^3/m、砂液比(1:15)^(1:17)。同时证明,精准定点有控压裂可在同等条件下将改造效果提高20%以上;在油藏埋深小于3500m、闭合应力低于55MPa的区块,石英砂可有效替代陶粒,具备进一步扩大应用规模的条件。

Partitioned volume fracturing has been applied in 118 wells in 11 tight conglomerate reservoirs in Mahu oilfield,proving the technique's suitability and operability.However,the best matching between rational fracturing parameters and optimal production results is still uncertain.In order to define the rational engineering technical parameters to guide the subsequent horizontal well fracturing design and also improve the comprehensive benefits of tight conglomerate reservoir development,the adaptability of horizontal well volume fracturing was studied through correlating the production data(e.g.,post-fracturing production and pressure)to the fracturing engineering parameters(e.g.,volume fracturing method,completion fracturing process,fracture parameters,fracturing scale and fracturing materials).The results show that the rational fracture spacing,sanding rate and sand-to-liquid ratio are 25-35 m,1.2-1.5 m^3/m,and 1:17-1:20 respectively for normal pressure reservoirs with poor physical properties,and about 40 m,1.0-1.2 m^3/m,and 1:15-1:17 respectively for abnormally high-pressure reservoirs with good physical properties.In addition,it is proved that precise fixed-point and controlled fracturing stimulation can increase post-fracturing production by more than 20%under the same conditions.In the block where the reservoir depth is less than 3500 m and the closing stress is lower than 55 MPa,quartz sand can effectively replace ceramsite,so it is promising for wider application.