鄂尔多斯盆地东缘煤系气合采接替方案优化
Productivity prediction and gas production technology of superimposed coal measure gas in the eastern margin of Ordos Basin
-
摘要: 鄂尔多斯盆地东缘发育叠置赋存煤系气储层,合采是解决单层产能低、综合效益差的有效方法。针对煤系气储层地质条件和开发过程中耦合流动机理研究不深入,难以揭示生产过程中耦合传质特征的问题,以临兴地区石炭二叠系煤系气储层为基础,通过多重相控建模技术,结合沉积微相划分和砂体控制程度分析,建立了多层叠置气藏高精细地质模型。在地质模型的基础上,基于静态产层组合分类标准,划分了有利开发气层组合。同时,研究根据煤层气和致密气微孔-裂隙-裂缝多尺度传质机理,建立了煤层气和致密气耦合传质链模型。研究结果揭示了互层连通、近距耦合和远距扰动的三重耦合作用下煤系气合采传质机理,其中耦合作用降低了煤层气和致密气合采的初期效果,但有利于长期稳产目标。进一步采用数值模拟方法,阐明了不同耦合关系条件下的动态合采特征,优化了静态产层组合与接替方案,提出了同井筒同压合采和分压合采条件下的合层排采工艺设计和设备选型方法,井筒工艺的研究确定了合采气水远距干扰的生产下限。研究区以山2段致密气作为气举气源,协同太2段煤层排水降压,煤层气解吸后可以实现“山2段致密气+太2段煤层气+本2段致密气”合采,接替以盒4段和盒8段致密气合采的方案最优,研究表明静态产层组合未考虑不同气藏生产过程中的动态干扰问题,产层组合优化应进行动态优选,探索了煤系气高效合采模式,可以为鄂尔多斯盆地东缘煤系气合采、增产等研究奠定理论基础,推动深层煤系气合理动用与高效开发。Abstract: Superimposed coal measure gas reservoirs are rich in the eastern margin of Ordos Basin. Combined production is an effective method to solve the problem of low single-layer productivity and poor comprehensive economic benefits. In view of the lack of in-depth research on the geological conditions of coal measure gas reservoir and the coupling flow mechanism in the development process, it is difficult to reveal the coupling mass transfer characteristics in the production process. Based on the Permo Carboniferous coal measure gas reservoir in the Linxing area, a high-precision geological model of multi-layer superimposed gas reservoir is established through the multiple facies control modeling technology, combined with sedimentary micro-facies division and sand body control degree analysis. Based on the geological model and the classification standard of static layer formation combination, the favorable development gas formation combination is divided. At the same time, the coupling mass transfer chain model of coalbed methane and tight gas is established according to the multi-scale mass transfer mechanism of coalbed methane and tight gas micropore-fracture-macrofracture. The research results reveal the mass transfer mechanism of coal measure gas combined production under the triple coupling action of interbedding connectivity, short-range coupling and long-range disturbance, in which the coupling action reduces the initial effect of the combined production of coalbed methane and tight gas, but is conducive to the long-term stable production goal. Furthermore, the numerical simulation method is used to clarify the dynamic combined production characteristics under the conditions of different coupling relations, optimize the horizon combination and replacement scheme of static production layers, and put forward the combined layer drainage process design and equipment selection method under the conditions of the same wellbore combined production and separate pressure combined production. The research on the wellbore process determines the production lower limit of the long-distance interference of gas and water in combined production. The study area takes the Shan 2 tight gas as the gas lift gas source, and cooperates with the drainage and depressurization of the Tai 2. After the desorption of the coal seam gas, the joint production of “Shan 2 + Tai 2 + Ben 2 s” can be realized, and the alternative scheme of the joint production of the He 4 and He 8 tight gas is the best. At the same time, the research shows that the static production combination does not consider the dynamic interference in the production process of different gas reservoirs, and the optimization method of production combination needs to be dynamically optimized from the static combination. The high-efficiency combined production model of coal measure gas is explored, which can lay a theoretical foundation for the research of combined production and production increase of coal measure gas in the eastern margin of Ordos Basin, and promote the rational use and efficient development of deep coal measure gas.