针对川东北超深沉凝灰岩储层水平井储层改造技术尚不完善的问题,开展了地质特征分析,物性参数及岩石力学参数测试,以及裂缝起裂、扩展特征研究。研究认为:川东北超深沉凝灰岩储层厚度较薄,属于低孔、低渗储层,黏土矿物含量高,脆性指数低,塑性极强,纵向上岩性复杂;储层破裂压力达到170 MPa及以上,应力差大于20 MPa,裂缝起裂及扩展难度大,施工压力高;储层岩石与酸液体系作用后易分散、垮塌,故宜采用固井滑套分段酸压完井方式,配套175 MPa压裂井口及装备,以提高施工排量,改善改造效果;可采用前置液态CO2、前置低黏液体、深穿透等孔径射孔、耐高温加重压裂液等手段降低破裂压力及施工压力;推荐以15%浓度盐酸作为酸液体系的基液,酸液体系须至少满足160℃流变实验及140℃动态腐蚀要求以及静置7 d后不出现弱交联、黏度增加的情况,剪切35 min黏度达到40 mPa·s及以上,同时要求少残渣、无析出、无结团。储层改造技术对策的研究对今后川东北超深沉凝灰岩储层的有效勘探与经济开发具有重要的借鉴和指导作用。

 Reservoir stimulation technology of horizontal wells in ultra-deep tuff reservoirs in northeastern Sichuan is not well established, then, analyzing geological characteristics, testing of physical parameters and rock mechanics parameters, and the research on the characteristics of fracture initiation and expansion are carried out to explore its effect on reservoir stimulation. The study shows that the ultra-deep tuff reservoir in northeastern Sichuan is thin in thickness, and belongs to low porosity and low permeability reservoir, featuring high clay mineral content, low brittleness index, strong plasticity, and complex lithology in the vertical direction of stratum; the fracture pressure of the reservoir is above 170 MPa, the stress difference is greater than 20 MPa, the fracture initiation and expansion are difficult, and at the same time, it is easy to cause high pumping pressure; as stratum is easy to disperse and collapse after the action of the reservoir rock and the acid system, so staged acid fracturing completion mode with cementing slip casing is mostly needed, which all need to be equipped with 175 MPa fracturing wellhead and equipment to enhance pumping rate and fracturing effect; measures such as pre-padding liquid CO2 and low-viscosity liquid, using deep penetration with aperture perforation and high-temperature resistant heavier fracturing fluid can lower the fracturing pressure and pumping pressure; it is recommended to use 15% hydrochloric acid as the base liquid of the acid fluid system. The acid fluid system must meet the requirements of 160℃rheological test and 140℃dynamic corrosion and no weak crosslinking and viscosity increase after standing for 7 days, and viscosity reaches 40 mPa·s and above after shearing for 35 min, as well less residue, no precipitation and no agglomeration. The stimulation technology for reservoir modification proposed in this paper is important reference and guidance for the effective exploration and development of ultradeep tuff reservoirs in northeast Sichuan in the future.