苏里格气田致密砂岩气藏多层分压开采面临的难题及对策

鄂尔多斯盆地苏里格气田发育二叠系山西组、石盒子组等多套含气层系,具有"一井多层、单层低产、横向非均质性强、渗透率低、压力低、丰度低"等特征,是典型的致密砂岩气藏。虽然历经多年的勘探开发,对该气田的地质认识不断深化,工艺技术创新发展和技术思路不断完善推动了该气田的规模上产,但随着勘探开发工作的持续推进,储层条件更加复杂,对多层分压开采技术提效降本提出了新的挑战。为此,在回顾总结苏里格气田多层连续分压开采技术发展历程的基础上,首先分析总结了攻关取得的认识与启示,认为目前已形成的机械封隔器分压和套管滑套分压两套主体分压技术是经济有效开发该气田的关键技术,压裂作业效率提高1倍以上,应用效果良好。进而把该气田开发面临的技术挑战归纳为"多层动用不充分、钻采工艺不满足气井全生命周期效益开发需要、分压工艺难以兼顾上古生界与下古生界气藏叠合开发需要"。最后结合苏里格气田的开发形势,探讨了解决上述难题的对策以及气藏多层分压开采技术的发展方向:①加强与井网匹配研究,提高储量动用程度及最终采收率;②优选改造层位,优化分压技术,提升多层动用开发效益;③系统优化钻采工艺技术,建立全生命周期小井眼提效降本新模式;④攻关适应于上、下古生界储层分压合求技术,以满足上、下古生界气藏叠合开发的需求。

Separate layer fracturing and multi-layer production of tight sandstone gas reservoirs in the Sulige Gas Field,Ordos Basin: Problems and countermeasures

In the Sulige Gas Field of the Ordos Basin, many sets of gas-bearing strata are developed, such as Permian Shanxi Formation and Shihezi Formation, and they are typical tight sandstone gas reservoirs with the characteristics of multiple layers in one well, low single-layer production, strong lateral heterogeneity, low permeability, low pressure and low abundance. After years' exploration and development, the geological conditions in the Sulige Gas Field are understood better and better, and the innovative development of processes and technologies and the continuous improvement of technical ideas promote scale production. With the continuous advance of exploration and development, however, the reservoir conditions become more complex, which brings new challenges to the efficiency increase and cost reduction of separate layer fracturing and multi-layer production technology. In this paper, the development history of separate layer fracturing and multi-layer continuous production technology in the Sulige Gas Field was reviewed, and the understandings and enlightenments obtained from the researches were analyzed and summarized. It is indicated that the existing separate layer fracturing technology consisting of two main parts (i.e., mechanical packer and casing sliding sleeve) is the key technology for the economic and efficient development of the Sulige Gas Field. It doubles the efficiency of fracturing operation, presenting a good application effect. Then, the technical challenges facing the Sulige Gas Field during its development were summarized as follows. Multi-layer production is insufficient, the drilling technologies cannot guarantee the benefit development in the whole life cycle of gas wells, and the separate layer fracturing technology can hardly give considerations to the congruent development of Upper Paleozoic and Lower Paleozoic. Finally, combined with the development situations of Sulige Gas Field, the countermeasures to above mentioned difficulties and the development direction of the separate layer fracturing and multi-layer production technology suitable for gas reservoirs were discussed as follows. First, strengthen the researches on well pattern matching and improve the reserves producing degree and the ultimate recovery factor. Second, select the layers to be transformed, optimize the separate layer fracturing technology, and improve the development benefit of multi-layer production. Third, optimize drilling and production technologies systematically, and establish a new efficiency increase and cost reduction model for the whole life cycle of slim holes. Fourth, research the separate layer fracturing and commingled production technology suitable for Upper and Lower Paleozoic reservoirs, so as to satisfy the congruent development of Upper and Lower Paleozoic gas reservoirs.