致密碳酸盐岩储层复合缝网酸压技术研究及矿场实践——以大牛地气田下古生界马五5碳酸盐岩储层为例

大牛地气田下古生界马五₅碳酸盐岩储层为低孔、低渗致密储层，储层丰度低，天然裂缝发育，常规酸压技术改造体积有限，水平井投产后产量递减快，稳产难度大。针对这些问题，分析了大牛地气田下古生界马五₅碳酸盐岩储层岩石脆性指数特征，开展了复合缝网酸压技术研究，采用“大排量前置液造缝+大规模胶凝酸缝网酸压+后置支撑剂保持裂缝导流能力”的设计思路，将水力加砂压裂与胶凝酸酸压复合，并优选复合缝网酸压线性胶前置液体系、胶凝酸体系及组合支撑剂体系，优化复合缝网酸压施工排量、施工液体用量比例及支撑剂用量等施工参数。矿场实践表明，该技术对大牛地气田下古生界马五₅碳酸盐岩致密储层具有较好的适用性和显著的改造效果，对大牛地气田下古生界气藏的大规模建产意义重大。

Study on composite fracture-network acid fracturing technology for tight carbonate reservoirs and its field application: a case study on Mawu5 carbonate reservoir of Lower Paleozoic in Daniudi Gasfield

In Daniudi gasfield, the Mawu₅carbonate reservoir of Lower Paleozoic is a low-porosity and low-permeability tight reservoir with low reservoir abundance and developed natural fractures.When conventional acid fracturing is applied in this reservoir, the stimulated volume is limited.The production after the commissioning of horizontal well declines fast and production stabilization is of high difficulty.To solve these problems, rock brittleness index characteristics of Mawu₅ carbonate reservoir of Lower Paleozoic in Daniudi gasfield were analyzed.Composite fracture-network acid fracturing technology was studied.The design concept of "create fracture by using large-displacement prepad fluid + perform large-scale acid fracturing of fracture network by using gelled acid + keep fracture conductivity by using post proppant" was adopted.Hydraulic sand fracturing was combined with gelled acid fracturing.Lineargel prepad fluid system, gelled acid system and composite proppant system were selected for composite fracture-network acid fracturing.And the construction parameters of composite fracture-network acid fracturing were optimized, including discharge capacity, operationalliquid dosage and proppant volume.This technology was actually applied to Mawu₅ tight carbonate reservoir of Lower Paleozoic in Daniudi gasfield.And it is better applicable to this reservoir and its stimulation effect is remarkable.This technology is of great significance to the large-scale productivity construction of Lower Paleozoic gas reservoirs in Daniudi gasfield.