超低渗透油藏水平井线注线采能量补充方法探索

Research on Line Injection and Line Production Energy Supplement Method for Horizontal Wells of Ultra-low Permeability Oil Reservoirs

鄂尔多斯盆地超低渗透油藏采用“点注面采”的水平井五点井网注水开发方式,表现出见效程度低、递减大等问题。为了强化注水、提高水驱见效,提出了水平井“线注线采”能量补充技术,以期实现井间互驱、缝间自驱和本井渗吸的目标。通过开展储层岩石力学测试,建立缝网分布预测模型,揭示了不同脆性指数及差应力下压裂缝的形态。脆性指数越接近0.5,两向应力差越大,裂缝带的长宽比越大、越扁平,越适合线注线采井网要求。对合水油田长6;油藏开展精细地质研究,优选Z288井南部为试验区,根据裂缝形态、储层特征等制定相应的井距、段间距、水平段、注水量等技术政策。通过在盆地合水地区开展井组试验,单井递减下降6.5个百分点,验证了该方法的合理性及可操作性,为超低渗透油藏水平井补能提供了有效的技术手段。

The “injection-on-points for areal production” method was used for the horizontal wells of the ultra-low permeability oil reservoirs in Ordos Basin. However, the horizontal wells under the five-point well pattern water injection development came across some problems, such as low efficiency and rapid declining. To enhance water injection for a higher water drive efficiency, the “line injection and line production” energy supplement technology for horizontal wells was proposed at the attempt to bring about inter-well mutual flooding, self-flooding between fractures and in-the-well imbibition. Based on the reservoir rock mechanical test, the fracturenetwork distribution prediction model was established to indicate the state of fractured seams under the different brittleness indexes and poor stress. The closer the brittleness is to 0.5 and the greater the two-way stress difference is, while the length-width ratio of the fractural belt is higher, flatter and more suitable to meet the requirements for line injection and line production. The Chang 6;oil reservoir of Heshui Oilfield was brought under fine geological study. The southern part of Z288 Well was selected as the experiment zone. The relative technological policies for well spacing, interval spacing, horizontal spacing and water-injection volume were formulated according to the fractural shape and reservoir characteristics. The well group test in Heshui area of the basin indicated that the single-well declining was reduced by 6.5 percent, confirming reasonability and operability of this method. Therefore, the technological method is effective to provide energy supplement for horizontal wells of ultra-low permeability oil reservoirs.