规模逸散后沦为“常压”

大约4.4亿年前，这里是一片汪洋。随着漫长的深水陆棚沉积，五峰组、龙马溪组等页岩相继成岩。

就生气条件而言，老厂坪似乎一枝独秀，这里的五峰组-龙马溪组TOC（总有机碳）含量大于4%的优质页岩段连续厚度达25米，丰富的有机质为页岩气的生成奠定了得天独厚的物质基础；主要为Ⅰ型有机质，有利于生成甲烷气；有机质热演化程度高，处于过成熟阶段。甲烷在这里大量生成并连续展布，催生了优质的原生页岩气藏。

保存条件是页岩气勘探的另一项重要指标。后期构造运动改造，包括地层断裂和剥蚀，都会改变气藏的保存条件，导致气藏散失。

渝东南地区经历多期构造运动的强烈改造，在老厂坪地区塑造出复杂的“两凹两凸夹一隆”的“马鞍形”构造。地质工作者将其形象地比喻为“原来浑然一体的仓廪，东厢塌了半边，西厢破了天窗，只剩中堂摇摇欲坠”。

地质运动改造叠加风化，导致渝东南的盆外页岩大量破裂，原本“家境殷实”的页岩气资源规模逸散后，沦为“常压”气藏，老厂坪因此被打入“高风险探区”之列。

距离老厂坪20多千米的焦石坝却因为地处四川盆地内部躲过了高烈度的地质运动改造，完整保存了储层，稳定保持高压，成就了涪陵页岩气田。

经过两年的反复勘查与论证，2020年3月2日，华东油气风险探井坪地1HF井在重庆市武隆区土坎镇清水村悄然开钻。但采用单管射流泵工艺排水采气，到2023年2月，坪地1HF井日均采气量仅7930立方米。

After the scale escapes to "normal pressure"

About 440 million years ago, it was a vast ocean. With the long deep-water shelf deposition, the shales of Wufeng Formation and Longmaxi Formation were formed successively.

In terms of gas generation conditions, Laochangping seems to have a unique position. The high-quality shale section with TOC (total organic carbon) content greater than 4% in Wufeng Formation and Longmaxi Formation here has a continuous thickness of 25 meters, which lays a unique material foundation for shale gas generation. It is mainly type I organic matter, which is conducive to the formation of methane gas. The degree of thermal evolution of organic matter is high and it is in the over-mature stage. Methane is produced in large quantities and distributed continuously here, giving birth to high-quality primary shale gas reservoirs.

Preservation condition is another important index of shale gas exploration. The late tectonic transformation, including formation fracture and denudation, will change the preservation conditions of gas reservoirs and lead to gas reservoir loss.

The complex saddle-shaped structure of "two concave, two convex and one uplift" was formed in Laochangping area after the intense transformation of multi-stage tectonic movement in southeast Chongqing. Geologists compare it vividly to "the original integrated granary, the east chamber has collapsed half, the west chamber has broken the skylight, and only the central hall is crumbling."

Geological movement transformation and superposition weathering caused a large number of shale fractures in southeast Chongqing. After the original shale gas resources of "rich family" were dispersed, they became "normal pressure" gas reservoirs. Therefore, Laochangping was classified as "high-risk exploration area".

Jiaoshiba, more than 20 kilometers away from Laochangping, has avoided the transformation of high-intensity geological movement because it is located in the interior of Sichuan Basin, completely preserved the reservoir, and maintained stable high pressure, which became the Fuling shale gas field.

After two years of repeated exploration and demonstration, on March 2, 2020, Pingdi 1HF well of East China oil and gas risk exploration well quietly began drilling in Qingshui Village, Tukan Town, Wulong District, Chongqing. However, using the single pipe jet pump process to drain gas production, by February 2023, the average daily gas production of Pingdi 1HF well is only 7930 cubic meters.