渤中25-1油田低渗透储层水平井分段压裂先导试验-《油气井测试》

文章信息/Info

Title:: Pilot test of horizontal well staged fracturing for low permeability reservoirs in BZ25-1 oilfield

Author(s):: LIU Peng; XU Jie; XU Gang; CHEN Yi; HAN Yaotu; Tianjin Branch of CNOOC Ltd., Tianjin 300459, China

Keywords:: BZ251 oilfield; lowpermeability reservoir; drilling platform; horizontal well; staged fracturing; casing completion

摘要:: 渤中25-1油田是海上典型的低渗透油田，存在埋藏深、岩性致密、异常高温高压、储层品质差，小层多跨度大、单井自然产能递减快、油藏整体采收率低等问题，难动用储量比例较大。以钻井平台为载体，中海石油首次对渤中25-1油田沙三段2口套管完井的水平井采用多级封隔器分段压裂技术开展大型加砂压裂先导性试验。分析了海上水平井大型加砂压裂施工作业难点与对策，通过压裂参数优化设计，使用哈里伯顿完井分段压裂工具分别对2口水平井成功完成了3～5段的加砂压裂改造。压后投产初期采用6 mm油嘴放喷排液，日产油分别为71.5 m3和92.8 m3，增产倍比是同区域邻井直井的5～8倍，压裂增产效果明显。渤中25-1油田水平井分段加砂压裂的成功，为海上低渗储层高效开发提供了可靠的技术保证，也为海上同类型油气藏勘探与开发提供经验。

Abstract:: BZ251 is a typical offshore low permeable oilfield with the characteristic of density lithology, buried depth, abnormally high temperature and high pressure, poor reservoir quality, small layers of large span, fast production decline of single well, low recovery factor and other issues, and difficult to produce reserves by a large proportion. Horizontal well staged fracturing is an important method to increase single well production in low permeability reservoirs. Selfelevating drilling platform as a carrier, the largescale sand fracturing field test of two casing completion wells was conducted in the E2s3 reservoir of BZ251 oilfield through horizontal multistage packer staged fracturing technology for the first time in domestic offshore. Offshore construction difficulties and technical countermeasures were analyzed, the optimization of completion string and fracturing parameters were carried out. Fracturing fluid was flew back to the hole through 6mm choke after fracturing, the daily oil flow rate was 715 m3 and 928 m3, the yield ratio has reached 5～8 times of vertical well in the same areas. The postfracturing production of two horizontal wells is obvious. The successful practice of horizontal well staged fracturing in BZ251 oilfield offered dependable technique for exploiting offshore low permeable reservoir, and valuable experience was provided for offshore exploration and development of the same reservoir.