Tectonic Evolution And Oil Enrichment Of Shu 25-shang 2 Blocks, Songliao Basin

Shu 25-Shang 2 Blocks are located in the east of Sanzhao sag, central depression area, Songliao basin,characterized by westward monocline. There are developed three third-grade structure units in the area, such as nose-like, Yushulin and Haojiafenfang structures. Fuyu & Yangdachengzi (FuYang) Oil layers as main target strata are mainly studied by comprehensive analysis of seismic interpretation, fracture system, tectonic evolution, oil-water relationship and petroleum enrichment in this paper.1. The structure in research area is characterized by low in southwest and high in northeast with few changes in stratums dip angles, in which FuYang reservoirs are characterized by good inheritance.2. Faults in the study area are normal faults which are classified into four zones in plans and display a horst-graben developing mode. Faults are classified as four stages, among which medium and late faults are developed, closely connected with oil-gas migration and accumulation.3. By using balanced cross-section technology, it is indicated that FuYang oil layers in Shu 25-Shang 2 Blocks began to deposit in Quantou period, and nearly formed in the end of Nenjiang period, experienced four tectonic evolution stages, such as steady subsidence stage of K1q3-K1q4, intensive extension stage of K2q- K2y1, steady subsidence stage of K2y2-K2y3 and reversion stage of late K2n.4. As faults developed very well in the study area, there mainly exist fault-trap reservoirs, followed by fault-lithologic reservoirs, and lenticular-shape lithologic reservoirs are few. Reservoir profile and the relationships between the planar oil and water indicate that small oil layers mainly accumulated in F-I and Y-I members, no unified oil-water interface occurs.5. The main reserving ways in select area are horst-reservoir, step-reservoir and graben–reservoir, among which the first one is best and the last one is worst. The hydrocarbon accumulation was migrated laterally from SanZhao depression. Oil Wells are mainly distributed along the fault zone nearby and more in west than the east, while the height of oil formation is on the contrary. Keywords: Fuyang reservoir; fault features; balancing cross-section; tectonic evolution; oil accumulation; Shu 25-Shang 2 Blocks...