超深断控凝析气藏注气提高凝析油采收率实验评价——以塔里木盆地顺北4号断裂带为例

Experimental assessment of enhanced gas condensate recovery by gas injection in ultra-deep fault-controlled condensate gas reservoirs： A case study of the No. 4 fault zone in the Shunbei area， Tarim Basin

胡伟 徐婷 杨阳 康志江 伦增珉 李宗宇 赵瑞明 张文学

Wei HU Ting XU Yang YANG Zhijiang KANG Zengmin LUN Zongyu LI Ruiming ZHAO Wenxue ZHANG

超深断控储集体具有板状巨厚特征，该类储集体多期流体组分重力分异显著。注气后流体相态特征与常规砂岩注气存在巨大差别，注气机理认识不清严重制约注气开发效果。通过开展高温、高压全视域可视化油气混相实验，在确定油气静态接触和混相特征前提下，采用竖直放置的未填砂的长填砂管模拟断控空腔型储集体，开展高液体凝析气反凝析后顶部注气和底部注气相态实验。根据长填砂管不同部位流体的多次多级取样分析，研究了两种注气方式下油-气接触方式和相态变化特征，确定了在重力和扩散作用下形成的垂向组分梯度。研究结果表明，混相压力下顶部注气油-气接触面积有限，导致油气组分交换速度缓慢及油相体积膨胀不足，无法形成混相。在重力和扩散作用下出现重烃下沉、轻烃上升的组分分层，长填砂管内底部凝析油中C烃类含量是顶部凝析油中的3.4倍。底部注气不但能够提高注气量、增大油-气接触面积和接触次数，形成多次接触局部混相，还能扩大凝析油组分动用范围，将凝析油中C烃类含量的垂向差异降至2.1倍。3轮累计底部注气凝析油采收率可达32.66 %，是顶部注气采收率14.13 %的2倍以上。

Ultra-deep fault-controlled reservoirs exhibit tabular shapes， extreme thickness， and significant gravitational differentiation in the components of multistage fluids. Their post-injection fluid phases differ greatly from those of conventional sandstone reservoirs. A lack of clear understanding of the mechanisms underlying gas injections in these reservoirs has severely hindered their gas injection performance. Using high-temperature and high-pressure full-field visualized experiments on oil-gas miscibility to clarify the static contact and miscible characteristics of oil and gas， we use a vertically placed empty， long sand-pack tube to simulate fault-controlled cavity-type reservoirs. For condensate gas with a high liquid content after retrograde condensation， phase behavior experiments are conducted with top and bottom gas injections. Based on the analysis of fluid samples collected at multiple stages at different positions along the long sand-pack tube， we investigate the contact modes and phase transition characteristics of oil and gas under both gas injection ways， and then clarify vertical compositional gradients formed under the action of gravity and diffusion. The results indicate that top gas injection leads to a limited oil-gas contact area under miscibility pressure， resulting in a low exchange rate of oil and gas components， insufficient volumetric expansion of oil， and ultimately the failure to form oil-gas miscible phase. Under the combined effects of gravity and diffusion， the dynamic cycle of “heavy drop and light rise” of components under the action of gravity and diffusion occurs， forming a vertical component gradient. Notably， the C content in the gas condensate at the bottom of the tube is 3.4 times that at the top. In contrast， bottom gas injection enhances both gas injection volume and the area and frequency of oil-gas contacts， facilitating multiple oil-gas contacts to develop local miscible phases， while expanding the range of recoverable gas condensate components， reducing the vertical difference in C content in gas condensate to 2.1 times. The cumulative recovery of gas condensate from three rounds of bottom gas injections is enhanced to 32.66 %， more than double that achieved through three rounds of top gas injections （14.13 %）.

10.11743/ogg20250217