人工气顶稳定气驱条件及其影响因素

为了开发倾斜断块油藏构造高部位的剩余油,提出了人工气顶稳定气驱(artificial gas cap stableflooding, AGCSF)方法。在明晰人工气顶稳定气驱机理的基础上,以注N_2形成人工气顶(artificial gas cap, AGC)为例,运用油气两相渗流理论和Dietz模式几何关系,明确了倾斜油藏人工气顶稳定气驱的条件,建立了保持气驱前缘界面稳定运移的临界速度模型。研究认为,气顶气驱速度小于临界速度是人工气顶稳定气驱的前提条件;重力、浮力、毛细管力、黏滞力和多相流动中所产生的各种附加阻力是人工气顶气驱前缘界面气油界面稳定的主要力学机制;原油相对渗透率、地层原油黏度、地层原油密度、地层次生气顶气(N_2)密度是影响临界速度的主要因素,且原油相对渗透率、地层原油密度越大,地层原油黏度、地层次生气顶气(N_2)密度越小,稳定气驱速度越大,越有利于人工气顶稳定气驱油。实例验证结果表明:新模型考虑的影响因素全面,且更为科学、合理、可靠;Y47X28断块古近系沙河街组二段1砂组油藏人工气顶稳定气驱速度小于其次生气顶气侵临界速度1.07×10~3m~3/d时可以实现稳定气驱。研究成果与认识可为倾斜油藏人工气顶稳定气驱开发关键技术的研发,为倾斜断块油藏阁楼油的高效开发提供理论基础和技术指导。

Theoretical Study on Interface Stability Conditions and Influencing Factors of Artificial Gas Cap Flooding in Fault Block Reservoirs with Inclination

In order to develop the crude oil in the middle and upper part of the fault block reservoir with dip angle, the method of artificial gas cap for stable flooding(AGCF) was presented. On the basis of clear mechanism,Staking the artificial gas cap(AGC) formed by N₂ injection as an example, using the theory of oil and gas two-phase seepage flow and geometric relationship of Dietz model, the interface conditions of AGCF in inclined reservoir were defined, and the critical velocity model for maintaining the stable migration of the gas flooding front edge interface was established. It is considered that That AGC gas drive velocity less than the critical velocity is the precondition of AGCF, and gravity, buoyancy, capillary force, viscous force and additional resistance in multiphase flow are the main mechanical mechanisms of gas-oil interface stability at the front edge of AGC under nitrogen injection for stable flooding, and the relative permeability of crude oil, formation oil viscosity, formation oil density and the formation density of secondary gas cap under nitrogen injection are the main influencing factors on the critical velocity. The bigger the relative permeability of crude oilSand formation oil density, the smaller formation oil viscosity and formation gas density are, the higher the stable gas flooding velocity is, and the more favorable it is for to AGC to form stable gas flooding. Through examples it proves that the new model takes into account a wide range of influencing factors, and is more scientific, reasonable and reliable. The results also show that the critical stable velocity of AGC gas flooding in the reservoir of Sand Group 1, section 2, Shahejie Formation, Paleogene in Ying 47X28 flaut block of Shengli Oilfield is 1.07×10^₅ m^₃/d. When the velocity of AGC gas flooding keeps lower than the critical stable velocity of AGC gas flooding, the reservoir can achieve stable gas flooding. This study provides theoretical basis and technical guidance for the efficient development of attic oil in inclined fault block reservoir and the development of key technologies for artificial gas cap stable gas drive development..