综合中国南方海相页岩气10年勘探开发成果与评价认识,针对云贵高原昭通探区山地页岩“高演化、强改造、剪应力”的特点及浅层页岩气扩散与渗漏时间长、保存条件最为关键等现实问题,对浅层页岩气甜点控制因素及其选区评价关键技术进行研究。2017—2018年,昭通国家级页岩气示范区率先在埋深700~2 000 m的太阳背斜上获得了浅层页岩气的勘探突破和规模探明地质储量,通过太阳背斜区浅层页岩气成藏条件分析及甜点控制因素研究,明确盆地外复杂构造区山地浅层页岩气成藏与产能潜力受控于5大要素：①富气区构造改造弱,整体保存条件良好,呈现典型压扭性改造圈闭赋存模式;②富气区处于超压状态,页岩含气量高;③富气区发育优质页岩,烃源条件优越;④富气区页岩储集层品质优良,Ⅰ类储集层占主导;⑤富气区页岩脆性矿物含量高,水平应力差小,易于体积压裂改造。昭通示范区太阳背斜区浅层页岩气的勘探突破和产能规模建设的创新实践及其形成的核心技术,具有重要的示范与引领作用。图23表5参42

昭通国家级页岩气示范区太阳背斜区浅层页岩气赋存与产能潜力受控于富有机质页岩储层厚度、物性、顶/底板封闭性、含气性及可压性五大地质要素，气藏显现出吸附气含量偏高、地层弱超压、初期产量相对偏低、气井产量稳定、递减率低等特征。通过创新集成，形成了浅层页岩气甜点选区评价技术、产能目标导向高效布井技术、国产近钻头地质导向技术、安全高效优快钻井技术、浅层页岩气体积压裂与精细控压排采等高效勘探开发关键技术，建立了太阳背斜区浅层页岩气开发示范基地，推动了昭通国家级页岩气示范区浅层页岩气勘探开发进程，引领了四川盆地以外中国南方复杂构造区海相山地浅层页岩气勘探开发进程。

中国南方浅层—超浅层页岩气分布广泛,资源量丰富。昭通页岩气示范区太阳页岩气田是率先突破且成功进行商业开发的整装规模浅层页岩气田。基于太阳气田的沉积地层条件、源-储条件、构造保存条件对其页岩气的富集成藏条件进行分析,总结了太阳地区浅层山地页岩气田的"四元"富集成藏规律,即沉积烃源条件好、优质页岩气储层条件好、储层体积压裂工程条件好、封存赋存条件好,其中,优质页岩气产层的主体岩相为深水滞留陆棚相沉积的富有机质生物硅质页岩。通过对太阳页岩气田的构造地质与成藏地质条件进行深入分析,结合气藏工程的认识,针对太阳背斜和海坝背斜建立了二者整体受"岩性岩相、储集孔隙、天然裂缝、构造应力、晚期泄聚"耦合机制控制的浅层—超浅层页岩气"自生自储+外源补给"复合型成藏模式,该模式是对太阳背斜工区"三维封存体系"浅层页岩气成藏模式的继承和发展。进一步地,通过优选有利区并明确资源情况,展望了中国南方浅层页岩气的资源前景。在昭通页岩气示范区,五峰组—龙马溪组一段1亚段Ⅰ+Ⅱ类储层整体较厚(平均厚度达30.1 m),在落实优质页岩储层分布的基础上,优选有利区面积超过550 km²,探明页岩气地质储量超过2 500×10⁸m³。此外,在四川盆地外围的东缘、南缘其他残留构造坳陷区,有20余口钻井展示出较好的浅层页岩气潜力,总资源量预计可达10×10¹²m³,这预示着在中国南方四川盆地外缘复杂构造残留坳陷区,浅层页岩气具有非常好的勘探开发前景。

Shallow/ultra-shallow shale gas is widely distributed and abundant in southern China. Taiyang shale gas field in Zhaotong National Shale Gas Demonstration Zone is the first integrated shallow shale gas field that has achieved breakthrough and successful commercial development. Based on the sedimentary conditions, source-reservoir conditions, and tectonic preservation conditions of Taiyang gas field, this paper analyzes the enrichment and accumulation conditions of shale gas in the study area, and summarizes the "four-element" enrichment and accumulation law of mountain shallow shale gas field in Taiyang area, involving good sedimentary source rock, high quality shale gas reservoir, good engineering conditions for reservoir volume fracturing, and good preservation conditions. The main shale lithofacies with high-quality gas production is biogenic (organic-rich)siliceous shale, which was deposited by shelf facies in deep water. By deeply analyzing the tectonic geology and accumulation geological conditions of Taiyang shale gas field, combined with the understanding of gas reservoir engineering, the self-sufficient and exogenous supply composite pattern of shallow/ultra-shallow shale gas accumulation controlled by the coupling of lithofacies, reservoir pores, natural fractures, tectonic stress, late hydrocarbon expulsion and accumulation has been established for Taiyang anticline and Haiba anticline. This model is the inheritance and development of the shallow shale gas accumulation model of "three-dimensional storage system" in the Taiyang anticline work area. Furthermore, based on optimizing favorable areas and identifying the resources, the paper looks forwards to the prospect of shallow shale gas resources in southern China. In Zhaotong National Shale Gas Demonstration Zone, Type Ⅰ and Ⅱ reservoirs from Wufeng Formation to sub-member 1 of Member 1 of Longmaxi Formation are relatively thick as a whole (with an average thickness of 30.1 m). Based on the distribution of high-quality shale reservoirs, the optimized favorable area is more than 550 km², and the proven geological reserves of shale gas are more than 2500×10⁸m³. In addition, in other residual structural depressions to the eastern and southern margins of Sichuan Basin, more than 20 boreholes exhibit good shallow shale gas potential, and the total resource is expected to reach 10 %×10¹²m³, which indicates that shallow shale gas has a very good exploration and development prospect in the residual depressions of complex structural area at the periphery area of Sichuan Basin, southern China.

基于四川盆地东南缘老厂坪背斜浅层常压页岩气井的钻井、测井、实验分析和试气试采等资料分析，开展浅层奥陶系五峰组—志留系龙马溪组页岩储集层地质特征、页岩气赋存机理与吸附解吸规律等研究，以揭示构造复杂区浅层常压页岩气富集高产规律。研究认为：①浅层常压页岩气优质页岩厚度、地球化学、物性、矿物组成等静态指标与中深层页岩气一致，但具有压力系数和含气量较低、吸附气占比高、地应力小、两向应力差异大等地质特点。②构造复杂区浅层页岩具有“总含气量较低（1.1~4.8 m³/t）、吸附气含量较高（2.5~2.8 m³/t）、敏感解吸压力低（1.7~2.5 MPa）、自封闭性好”的气体赋存特征。③页岩吸附气富集主要受有机质丰度、地层温度和压力等因素控制，有机质丰度和地层压力越高、地层温度越低，吸附能力越强，越有利于吸附气赋存。④浅层常压页岩气敏感解吸压力较低，降低流压至敏感解吸压力以下，可实现吸附气快速解吸产出。⑤PD1井的勘探突破揭示以吸附气为主的浅层构造复杂区仍能形成规模页岩储集层，证实四川盆地周缘浅层常压页岩气具有良好的勘探潜力。

昭通示范区太阳浅层页岩气田自规模开发以来，一直存在着较大井距、单一靶体的开发方式所带来的低储量动用率和低采收率的问题，同时也给后期井网加密或调整留下严重的工程隐患。为此，在太阳浅层页岩气田部署实施了TYH11井组小井距立体开发试验井组，以地质、钻井、压裂、试采资料为基础，以水力裂缝模拟和生产数值模拟为手段，对该井组开展“部署—钻井—压裂—排采—产能”全过程的评价。研究结果表明：太阳气田上奥陶统五峰组—下志留统龙一1亚段内Ⅰ+Ⅱ类储层均具有高产条件，具备纵向多靶体动用基础；形成了钻井、压裂、返排测试全过程的工程技术序列，可支撑小井距立体开发井组顺利实施；小井距立体开发方式有效提高储量动用率23.0%、提高采收率11.0%；天然裂缝沟通造成井组内部以及与邻井的压窜干扰，对老井产量造成较大负面影响；邻井组已生产老井周边地应力场变化会加剧井间干扰，建议新投井与老井至少保持380～500m井距。该研究成果为昭通示范区太阳气田浅层页岩气立体开发的推广应用、开发方案设计、开发政策制定和规模效益开发奠定了基础。

Since the large-scale development of Taiyang Shallow Shale Gas Field in Zhaotong demonstration block, there has been always problems such as low reserve production rate and low recovery factor caused by the development mode of large well spacing and single target layer, which also bring severe engineering risks for the later well pattern infill or adjustment. Therefore, pilot well group with small well spacing is deployed and implemented in Platform TYH11 for stereoscopic development of Taiyang Shallow Shale Gas Field. Based on hydraulic fracture simulation and production numerical simulation methods, the whole process evaluation of “pilot well deployment-drillingfracturing-production-production capacity” is conducted by applying geological, drilling, fracturing and production test data. The study results indicate that : (1) ClassⅠ+Ⅱ reservoir in first sub member of the first member of Longmaxi Formation (Long 11 sub member) in the Upper Ordovician Wufeng- Lower Silurian has conditions for high-yield production and basis for multi-target production in vertical; (2) The engineering technology series have been developed for the whole process of drilling, fracturing and well testing, which enable the successful implementation of stereoscopic development well groups with small well spacing; (3) The stereoscopic development mode with small well spacing supports to effectively increase the reserve production rate by 23.0% and the recovery factor by 11.0%; (4) The communication of natural fractures causes pressure channeling interference within the well group and with adjacent wells, which greatly impacts on the production of old wells; (5) The frac-hit is aggravated by the change of in-situ stress field around the adjacent old producing wells, so it is recommended to keep a well spacing of at least 380-500 m between the new well and the old well. The study results lay a foundation for the promotion and application, overall development plan design, development policy formulation, and large-scale and beneficial stereoscopic development of Taiyang Shallow Shale Gas Field in Zhaotong demonstration block.

综合运用有机超显微组分识别、聚焦离子束扫描电镜、高温高压等温吸附和页岩气稀有气体同位素年龄测定等技术,深入研究四川盆地涪陵地区页岩气主力产层上奥陶统五峰组—下志留统龙马溪组的烃源品质、有机质孔隙发育特征、页岩气赋存形式和封存机制。结果表明：①五峰组—龙马溪组富有机质页岩主要形成于表层水生产力高、底层水缺氧的沉积环境,TOC值呈两段式分布,下段TOC≥3%,主要由浮游藻类、疑源类、细菌和笔石等成烃生物及残留沥青组成,其中笔石是TOC值的主要贡献者之一,但页岩气主要来自浮游藻类、疑源类等富氢富脂质有机质及由其生成的液态烃裂解。②有机质孔隙主要发育在固体沥青和富氢有机质中,是页岩气的主要储集空间。笔石等大量有机质呈纹层状、堆积式分布,为页岩气提供了更多的储存空间和各类孔隙连通、流体流动的优势通道。③涪陵页岩气处于超临界状态,以游离气为主。页岩气封闭体系的形成时间与生气高峰期之间的有效匹配,以及后期构造活动对页岩气封存条件的改造程度低是复杂构造区高热演化页岩气滞留富集的关键,页岩的吸附作用、毛管封闭以及低速扩散形成了页岩气微观滞留富集机制。可见,复杂构造区高热演化海相页岩气的形成与富集受缺氧的沉积环境、优质的烃源品质、优越的储集空间和良好的封存条件综合控制。图10表1参35

The source rock quality, organic pore structure, occurrence state and sealing mechanisms of shale gas in the Ordovician Wufeng-Longmaxi Formation (O₃w-S₁l), Fuling region, Sichuan Basin were studied using ultra-microscopic organic maceral identification, FIB-SEM, high temperature/pressure isothermal adsorption and isotopic age dating of noble gas. The results show that: (1) O₃w-S₁l organic-rich shale was mainly formed in a sedimentary environment with high productivity in surface water and hypoxia in bottom water, it can be divided into two sections according to TOC, of which the lower section (TOC≥3%) is mainly composed of graptolite, phytoplankton, acritarch, bacteria and solid bitumen, among them, graptolite is the main contributor to TOC, but the shale gas is mainly derived from phytoplankton, acritarch and other hydrogen-rich organic matter, as well as the pyrolysis of liquid hydrocarbons produced by this kind of organic matter. (2) Organic pores, as principal reservoir space for shale gas, exist in hydrogen-rich organic matter and solid bitumen. The graptolites and plenty of other organic matter stacking distribution in lamina provide more reservoir space for shale gas, and effective pathways of connected pores for fluid flow. (3) Shale gas in Fuling region is in supercritical state and dominated by free gas; the match of formation time of closed shale gas system and gas-generation peak, as well as slight alteration degree of sealing conditions in the later stage, are key factors controlling the retention and accumulation of shale gas in the regions with high thermal maturity and complex structural areas; adsorption, capillary sealing and slow diffusion of shale are the main microscopic mechanisms for the retention and accumulation of shale gas. It thus can be seen that the generation and accumulation of marine shale gas with high thermal maturity in complex structure areas is controlled jointly by anoxic depositional environment, excellent hydrocarbon rock quality, superior reservoir space and favorable sealing conditions.

针对上奥陶统五峰组—下志留统龙马溪组优质页岩生储机理不清的问题,以四川盆地五峰组—龙马溪组深水陆棚相优质页岩为研究对象,结合页岩气形成地质条件和实验分析模拟,从岩石学、矿物学、地球化学等多方面对页岩成烃、成储机制及内在耦合关系等进行分析。结果表明,四川盆地五峰组—龙马溪组优质页岩热演化程度高、生烃强度大、物质基础好,具有良好的顶底板条件;深水陆棚相优质页岩不仅具有高生物成因硅、高有机碳含量,而且具有相对高孔隙度耦合特征。研究认为：①四川盆地五峰组—龙马溪组高演化深水陆棚相优质页岩保存条件好,早期原油滞留效率高,其气源主要来自原油滞留裂解气。②深水陆棚相生物成因的硅质（蛋白石A）,在埋藏成岩早期转化成高硬度晶态石英,伴生形成大量微米级粒间孔,而生物成因的硅质格架抗压性强,为优质页岩储集层早期原油充注及纳米级蜂窝状有机孔的发育和保持提供了空间和保护,是有机孔得以保存的关键因素。③五峰组—龙马溪组优质页岩脆性好,均质性强,微米级硅质粒间孔与纳米级有机孔共生,是压裂形成复杂缝网、硅质粒间纳米级有机孔实现高效连通的关键,有利于页岩气高产、稳产。图12表2参28

基于对中国南方和美国页岩气地质特点的分析,探讨了中国式页岩气成藏富集主控因素及勘探开发的关键问题。中国式页岩气地质特点包括：构造演化阶段多,构造类型复杂,断裂发育,页岩层系连续分布面积小,寒武系、志留系两套主要页岩层系现今的热演化程度和埋深没有对应关系。通过对影响页岩气富集的主要因素（裂缝、构造类型、页岩气运移、含气量等）的分析和探讨,提出了中国式页岩气的富集机理：“沉积相带、保存条件”是控制页岩气成藏的主要因素,控制页岩气选区;“构造类型、构造作用”是控制页岩气富集的主要因素,控制甜点区的选择。中国页岩气勘探开发下一步攻关方向为：①与美国页岩气发展刚好相反,中国页岩气勘探开发要从超压区向常压区甚至低压区发展;②四川盆地内应从中深层向深层发展,开展埋深大于4 000 m页岩层系成藏富集机理,特别是水平井压裂工艺技术的攻关;③借鉴海相页岩气的勘探开发经验,推动海陆过渡相、陆相页岩气的发展。图4表3参33

By analyzing geological characteristics of shale gas in Southern China and the United States, main factors controlling the accumulation and key issues in the exploration and development of shale gas in China have been examined. The geological characteristics of shale gas in China include multi-stages of tectonic evolution, complex structure types, abundant faults, small continuous distribution area of shale formations, and no corresponding relationship between current thermal evolution degree and current burial depth of two main sets of shale formations (the Cambrian and Silurian). According to the analysis of the factors affecting shale gas enrichment such as fracture, tectonic type, shale gas migration, and gas content etc, the enrichment mechanisms of shale gas in China are: “sedimentary facies and preservation condition” are the main reservoir-controlling factors affecting the accumulation of shale gas, and “structure types and tectonism” are the main factors controlling the enrichment of shale gas in China; the former factors define shale gas plays, and the latter ones determine the position of sweet spots. The future research directions of shale gas in China are: firstly, contrary to the shale gas development in the United States, shale gas exploration and development in China should extend from the overpressure to normal pressure, and even low pressure areas; secondly, shale gas exploration in the Sichuan basin should extend from middle-deep to deep formations, studies should be done on the shale gas enrichment mechanism and accumulation models in formations more than 4 000 m deep, and horizontal well fracturing technology for these formations; thirdly, the development of transitional facies and continental facies shale gas should be brought along by drawing on exploration and development experience of marine shale gas.

Based on the shale depositional background and environment, structural reformation process, reservoir filling characteristics and records of Wufeng Formation-Longmaxi Formation in Zhaotong Demonstration Area, combined with the analysis of shale hydrocarbon generation history, it is clear that the distribution of shale gas favorable area in the demonstration area is mainly controlled by three factors: sedimentary facies, deformation strength during the reformation period and sealing performance during the preservation period. According to the current shale gas preservation unit, shale gas reservoirs in the demonstration area are divided into three types: anticline, syncline and slope. The anticline type (Taiyang, Haiba, etc.) is mainly enriched in crude oil-cracked gas, and the main controlling factors are the strength of later transformation and the sealing performance of the preservation unit, and the favorable areas are mainly isolated and inherited anticlines. The syncline type (Luochang-Jianwu, Luobu, etc.) is mainly enriched with kerogen pyrolysis gas, and the main controlling factors are sedimentary facies and the sealing performance of preservation units, and the favorable areas are mainly wide and gentle inherited synclines, most of which are continuously distributed. The slope type (Huangjinba-Zijinba zone of the south wing of Luochang-Jianwu compound syncline and Yunshanba transition area between Taiyang and Haiba anticline, etc.) is characterized by enrichment of mixed source gas (crude oil-cracked gas and kerogen pyrolysis gas), and the favorable areas are mostly distributed along the wing transitional zone between anticline and syncline.

Wufeng Formation-Longmaxi Formation is an important sequence in Sichuan and Chongqing area for shale gas exploration. Based on the analysis of chemical component and stable carbon isotope composition of the shale gas acquired by desoption experiments on Wufeng-Longmaxi Formation shale cores from the Souteastern Chongqing, it is discussed for the genetic type of shale gas and the reason for alkane carbon isotopic reversal. The results showed that the methane content is high with a value from 94.33, to 98.96, in Longmaxi Formation shale gas, and the non-hydrocarbon content is low, mainly including N2 and CO2. The drying coefficient is more than 0.98, indicating typical dry gas. The values of carbon isotopes of methane and ethane are -49℅~-24.47℅ and -39.4℅~-29℅ respectively, and the carbon isotopes of C1 to C3 alkane in Well Y1 with good gas-bearing presents complete reversal, but Well Y2 presents normal. According to the statistical criteria,natural gas in the Southeastern Chongqing area is derived from the sapropelic source rocks, which is a result of high-temperature pyrolysis. It is a mixing product of pyrolysis of kerogens and secondary pyrolysis of crude oil,with obvious features of secondary pyrolysis of oil. The reason for complete reversal of carbon isotopic in Well Y1 is the mixing of two gases. Perhaps, it has some relationships with high production of shale gas.

为了研究四川盆地长宁地区志留系龙马溪组页岩气碳同位素组成特征，以及该区过成熟页岩气碳同位素组成倒转成因，对长宁地区15个页岩气样的地球化学特征进行综合分析。通过测试烷烃气组分和碳同位素组成，结合四川盆地涪陵和威远地区龙马溪组页岩气碳同位素组成研究，长宁地区龙马溪组页岩气CH4含量为97.11%～99.45%，湿度平均为0.49%，δ13C1值异常重，平均可达?28.2‰，δ13C2平均为?33.2‰，气源母质为腐泥型，属于油型干气。随热演化程度增加，页岩气湿度逐渐降低，甲烷碳同位素组成整体变重，乙烷和丙烷碳同位素组成会发生反转，但长宁地区过成熟页岩气的乙烷和丙烷碳同位素组成处于反转后阶段，不会持续变重。综上，长宁地区页岩气甲烷碳同位素组成的重异常、碳同位素（δ13C1>δ13C2>δ13C3）的完全倒转现象，主要由过成熟阶段的二次裂解效应及乙烷瑞利分馏条件下与水、含铁金属发生反应等次生作用所导致，高地温条件也是重要影响因素之一。图7表1参39