一种用于高压 CO₂环境中的强凝胶封窜剂的研发与性能评价

Development and Performance Evaluation of a Strong Gel Used for Plugging Channeling Agent under High Pressure CO₂ Environment

曹 耐 董平川 林士尧 丛海龙 王 娟 刘潇潇

CAO Nai DONG Pingchuan LIN Shiyao CONG Hailong WANG Juan LIU Xiaoxiao

为了封堵裂缝性特低渗油藏中的高压气窜通道，研发了一种用于高压 CO2环境下的配方为 2%改性纤维素+2%丙烯酰胺+0.1%交联剂（N’N-亚甲基双丙烯酰胺）+0.03%～ 0.1%引发剂（过硫酸盐）的改性纤维素类强凝胶封窜剂，并考察了所形成凝胶的黏弹性、热稳定性和封堵性。研究结果表明，堵剂在 10 MPa的高压 CO2环境下成胶时间为 6～ 24 h，凝胶黏度为 18×104 mPa·s，所形成的凝胶具有很高的强度，在 1 Hz下弹性模量为 3500 Pa、耗损模量为 500 Pa。该凝胶能在高压气体环境下长期稳定存在。在高压气体中放置 120 d后由于酸性作用和气体穿透作用，凝胶的性能相对减弱、其微观结构变得相对稀疏，但仍具有半固体的性质，弹性模量为 2100 Pa、耗损模量为 280 Pa。封堵前裂缝性岩心在出口端的气体流速高达 23000 mL/min，而封堵后裂缝性岩心在出口端气体流速降至 830 mL/min，接近于均质岩心的气体流速（640 mL/min）。该纤维素凝胶可被用于封堵裂缝性油藏中的高压气窜通道。图 10表 1参 19

In order to plug the gas channeling passage in the fractured reservoir，a modified cellulose gel used as plugging channeling agent at the high-pressure CO2 environment，composed of 2% modified cellulose + 2% acrylamide + 0.1% crosslinking agent（N，N'-methylenediacrylamide）+ 0.03% ～ 0.1% initiator，was developed，and the viscoelasticity，thermal stability and plugging performance of the gel was investigated by bottle test，SEM，and rheological test，respectively. The results showed that under the high-pressure CO2 environment of 10 MPa，the gelling time was controlled from 6 to 24 h，the viscosity of the gel could achieve 18×104 mPa·s，and the elastic modulus and loss modulus of the gel was 3500 Pa and 500 Pa at 1 Hz，respectively. The gel could be stable under the high pressure gas environment for a long time. After placed for 120 d，the performance of the gel was relatively weakened due to the effect of acidification and gas penetration，the microstructure became relatively sparse，however，it still had the nature of the semisolid and the elastic modulus and the loss modulus was 2100 Pa and 280 Pa at 1 Hz，respectively.After plugging，the gas flow rate decreased from 23000 mL/min to 830 mL/min，which was close to the homogeneous core gas velocity（640 mL/min）. The cellulose gel could be used to plug the gas channeling under high pressure CO2 environment in the fractured reservoirs.