长庆超低渗透油藏低产水平井重复改造技术研究及应用

Study on repeated stimulation technology and its application to in low-yield horizontal wells in ultra low permeability oil reservoirs, Changqing Oilfield

受储层致密低压、完井改造程度低、长期注采驱替难以建立等因素影响,鄂尔多斯盆地部分水平井产量递减大而低产。通过对水平井典型注采井网的生产动态进行历史拟合,研究了油藏压力和剩余油分布特征。以扩大储层改造体积、增加裂缝复杂程度、恢复缝网导流、解除深部堵塞和提升地层能量为目的,集成体积压裂与补充能量为一体进行重复改造设计,形成了水平井"高排量注入、两级暂堵升压、多功能压裂液、压后关井扩压"的分段补能体积复压工艺模式和配套的压缩式双封单卡组合管柱。优化施工排量为4~6 m^3/min,缝口缝内两级暂堵转向,单段液量为800~1 000 m^3,单段压后关井1~2 d。在鄂尔多斯盆地超低渗透油藏开展了5口水平井现场试验,单井补能体积复压5~6段,井均日产油量由1.6 t提高至6.2 t,达到了本井投产初期产量,与同区块常规复压井相比日增油提高了1倍。井组地层能量上升2~4 MPa,1年累计增油量超过1 200 t,与本井初次压裂投产相比年递减率降低38%。该技术对其他非常规储层提高水平井老井产量及最终采出程度有一定的借鉴。

In the Ordos Basin,the production rate of some horizontal wells declines significantly to the low value for the reservoirs are tight with low pressure,the completed wells are less stimulated and long-term injection and production displacement cannot be established easily.In this paper,history match was performed on the production performance of typical injection-production pattern of horizontal well to investigate the oil reservoir pressure and remaining oil distribution characteristics.Volumetric fracturing and energy complement was integrated for repeated stimulation design so as to enlarge reservoir stimulation volume,increase fracture complexity,recover fracture network diversion,remove deep blockage and improve formation energy.Then,the technological model for the staged energy complement and repeated volumetric fracturing of horizontal well was established,i.e.,“high flow rate injection,two-stage temporary plugging for boosting,multi-functional fracturing fluid,and post-fracturing shut in for diffusion”,and its support compression string with twin packer and single slip was developed.The optimized flow rate is4-6m3/min,there is two-stage temporary plugging for diversion at the opening and inside of fracture,the fluid volume in each section is800-1000m3and shut in period after fracturing of each section is1-2d.It was tested on site in5horizontal wells in ultra low permeability oil reservoirs in the Ordos Basin.Energy complement and repeated fracturing is carried out at5-6sections in each well,and average daily oil production of each well is increased from1.6t to6.2t,which is equal to its production rate at the early stage of commissioning.And its oil increment is100%higher than that of the wells which are treated with the conventional repeated fracturing in the same block.The formation energy of the well group rises by2-4MPa,the cumulative oil increment is over1200t one year,and yearly decline rate is38%lower than that after the initial fracturing of this well.This technology can be used as the reference for increasing the production rate and ultimate recovery factor of old horizontal wells in unconventional reservoirs.