我国陆上最大的整装致密气田——苏里格气田，经过30多年的规模开发，储层劣质化、碎片化、复杂化特征明显。为进一步提高气田老区单井产量、降低钻完井成本，长庆油田不断挖掘低产低效井和老井的潜力，在苏里格气田开展了多井型老井侧钻等进攻性挖潜措施试验，并取得一定效果。但随着改造强度的逐步加大，常规胍胶压裂工艺需要配套大量清水，而西北地区水资源缺乏，加之老区开采时间较长，储层压力场环境发生变化，普遍表现出地层压力低的特征。

针对常规压裂工艺液量大、低地层压力系数下储层保护和压裂后液体返排难度大的难题，长庆油田加大科研攻关力度，以问题为导向，坚持地质工程一体化研究思路，结合低压致密老气藏易发生水锁伤害的储层特征，通过创新设计氮气泡沫压裂工艺流程、泡沫发生增强器、小容积高转速混砂车和研发配伍性优良的泡沫压裂液体系，形成了以“氮气泡沫少水挟砂+高砂浓度高效造缝+多尺度支撑高导流”为核心的氮气泡沫压裂工艺技术。

同时，科研人员利用低渗透油气田勘探开发国家工程实验室平台，进一步深化泡沫压裂增产机理研究。科研人员通过大物模、数值模拟实验，研究不同介质条件下气体增能压裂裂缝扩展规律，研发低成本泡沫压裂液体系，构建低压致密砂岩储层复杂缝网，补充地层能量、降低储层敏感性伤害，继续探索低压气藏气体增能体积压裂技术。

Sulige Gas field, the largest integrated tight gas field on land in China, has been developed on a scale for more than 30 years, and the reservoir is characterized by inferior quality, fragmentation and complexity. In order to further increase the output of a single well in the old area of the gas field and reduce the cost of drilling and completion, Changqing Oilfield has continuously tapped the potential of low-yielding and low-efficiency Wells and old Wells, and carried out the test of offensive potential exploitation measures such as multi-well sidetracking of old Wells in Sulige gas field, and achieved certain results. However, with the gradual increase of the transformation intensity, the conventional guanidine gum fracturing process needs to support a large amount of clean water, and the shortage of water resources in Northwest China, coupled with the long mining time in the old area, the reservoir pressure field environment has changed, and generally shows the characteristics of low formation pressure.

In view of the difficult problems of reservoir protection and fluid flowback after fracturing under large fluid volume in conventional fracturing process and low formation pressure coefficient, Changqing Oilfield has intensified scientific research efforts, problem-oriented, adhered to the integrated research idea of geological engineering, and combined with the reservoir characteristics of low pressure tight old gas reservoirs prone to water lock damage. Through innovative design of nitrogen foam fracturing process flow, foam generation booster, small volume and high speed sand mixer and research and development of excellent compatibility of the foam fracturing liquid system, the nitrogen foam fracturing technology with "nitrogen foam with less water sand + high sand concentration and efficient fracture + multi-scale support and high conductivity" as the core has been formed.

At the same time, researchers made use of the platform of the National Engineering Laboratory for Exploration and Development of low permeability oil and gas fields to further deepen the research on the stimulation mechanism of foam fracturing. Through large physical models and numerical simulation experiments, researchers studied the fracture propagation law of gas enhanced fracturing under different media conditions, developed low-cost foam fracturing liquid systems, constructed complex fracture networks of low pressure tight sandstone reservoirs, supplemented formation energy, reduced reservoir sensitivity damage, and continued to explore gas enhanced volumetric fracturing technology for low pressure gas reservoirs.