Research Article
Early Paleozoic Extension-Compression Transition and Formation of a Paleo-Oil Reservoir System in the NW Sichuan Basin: Implications for Deeply Buried Hydrocarbon Accumulation
Figure 12
Deeply buried reservoir characteristics of the Dengying and Qixia formations. (a) CS-1 well that is located between 8161.07 and 8161.20 m and consists of algal-laminae stromatolite dolomite (Zn2dn4). (b) CS-1 well that is located between 8162.04 and 8162.15 m and consists of algal-dolarenite and algal irregular nodule dolomite (Zn2dn4). (c) CS-1 well that is located between 8160.29 and 8160.36 m and consists of karst holes that are formed near the unconformity at the top of the Dengying Fm (Zn2dn4). (d) CS-1 well that is located between 8157.96 and 8158.07 m and consists of karst holes that are formed by strong paleokarst weathering at the top of the Dengying Fm (Zn2dn4). (e) CS-1 well that is located between 8157.18 and 8157.34 m and consists of fine crystalline dolomite with bitumen and saddle-shaped dolomite that fills in super large intercrystalline pores and intercrystalline dissolved pores. The traces of bitumen that are notably disturbed and broken (Zn2dn4) into pieces. (f) ST-3 well, which is located between 7433.72 and 7433.85 m, consists of dolomitic leopard limestone (P2q). (g) ST-12 well that is located between 7065.48 and 7065.63 m and consists of the bedrock is micrite. Gray leopard dolomicrite that is formed after partial dolomitization (P2q). (h) ST-12 well that has characteristics of methane-bearing inclusion in coarse-grain dolomite of the Qixia Fm. (i) ST-12 well that is located between 7050.24 and 7050.34 m and consists of gray micrite with developed fractures (P2q2). (j) ST-12 well that is located between 7057.50 and 7057.72 m and consists of micrite with corrosion pores and a large amount of bitumen infill. (k) ST-12 well that is located between 7059.22 and 7059.28 m and consists of two-stage dolomitization, the early stage is dolomicrite and later recrystallized to form gray-white, medium-coarse, and grained dolomite (P2q2).