川中地区震旦系灯影组碳酸盐岩天然裂缝特征及其对气井产能影响

四川盆地中部地区震旦系灯影组碳酸盐岩是中国深层-超深层油气勘探开发的热点领域，储层中普遍发育不同类型、不同尺度的天然裂缝，对储层渗流规律和气井产能具有重要影响。以川中地区高石梯-磨溪区块灯影组四段（简称灯四段）为例，综合利用岩心、薄片、成像测井、分析测试及试井分析等资料，在明确天然裂缝成因类型和发育特征的基础上，分析控制天然裂缝发育的主要地质因素，并探讨天然裂缝对气井产能的影响。研究结果表明：(1)高石梯—磨溪地区灯四段碳酸盐岩储层主要发育构造裂缝和成岩裂缝，其中构造裂缝包括剪切裂缝和张性裂缝，成岩裂缝主要为层理缝和缝合线；(2)构造剪切裂缝为灯四段储层主要裂缝类型，以高角度裂缝为主，裂缝走向主要包括NNW-SSE向、近EW向、NE-SW向和近SN向；(3)裂缝有效性受控于裂缝形成时间、胶结和溶蚀作用、裂缝产状及现今地应力，NNW-SSE向和近EW向剪切裂缝有效性相对较好；(4)裂缝发育程度与储层岩性、岩石力学层厚度及断层等密切相关，泥晶云岩中裂缝更为发育，随岩石力学层厚度增加，裂缝密度减小、规模增大，主干走滑断层附近，尤其是断层端部和叠合区域，裂缝发育程度更高；(5)裂缝发育程度和有...

Characteristics of natural fractures in carbonate reservoirs and their impacts on well productivity in the Sinian Dengying Formation， central Sichuan Basin

Carbonate reservoirs in the Sinian Dengying Formation， central Sichuan Basin， are a hot spot for hydrocarbon exploration and development in deep and ultra-deep sequences in China. Multi-type and multi-scale natural fractures are widely seen in the Dengying reservoirs， and of significant impacts on the seepage flow pattern and well productivity. In this study， the genetic types and developmental characteristics of natural fractures in the fourth member of Dengying Formation （Deng 4 Member）， Gaoshiti-Moxi area， are clarified utilizing the cores， thin sections， image logs， experimental tests and production testing data. Major geological factors controlling the development of natural fractures are used to analyze the impact of natural fractures on well productivity. Results show that natural fractures in the Deng 4 Member reservoirs in Gaoshiti-Moxi area are mainly of tectonic and diagenetic types. The tectonic fractures can be divided into shear fractures and tension fractures， and the diagenetic fractures are mainly bedding fractures and stylolites， among others. The shear fractures dominate the Deng 4 Member reservoirs， and are mainly of high-angle ones and striking in the NNW-SSE， nearly EW， NE-SW and nearly SN directions. Factors controlling the shear fracture effectiveness include the timing of fracture formation， cementation， dissolution， fracture occurrence and current in-situ stress. The shear fractures in NNW-SSE and nearly EW orientation are more effective than others. The development degree of shear fractures is closely related to the lithology， mechanical layer thickness and faults. The shear fractures are more highly developed in micritic dolomites， and their density decreases and scale enlarges along with the increasing thickness of mechanical layers. The shear fractures near the main strike-slip faults， in particular within the tip and superimposed part of faults， are better developed. The development degree and effectiveness of fractures jointly determine gas well productivity. The effective fractures in different occurrences and scales can form fracture network， and get relatively isolated pores interconnected， which greatly improves the seepage capacity of reservoirs and elevate well productivity. In the Deng 4 Member reservoirs of Gaoshiti-Moxi area， the shear fractures in NNW-SSE and nearly EW orientation are of stronger ability to enhance reservoir permeability， and make greater contribution to the improvement of well productivity.