| Numerous research documents have shown divergent viewpoints on the Lower Triassic Feixianguan oolitic beach reservoir, especially on dolomitization, pore types and pore genesis, in the isolated platform in northern Sichuan Basin. Based on data from outcrops, drilling cores, and reservoir characteristics, it is indicated that the reservoir mainly consists of remnant oolitic micritic crystalline dolostone and fine crystalline dolostone. Intergranular pores and oomoldic pores are common types of reservoir space. The controlling factors of reservoir genesis are sedimentary microfacies, mineral component of ooids and early meteoric leaching. The microfacies is the basic for development of intergranular pores; the mineral composition of ooids and the meteoric leaching are the crucial for forming oolimoldic spaces. Seepage reflux dolomitization plays an important role in preserving early pores. It contributes increasing rock strength and repressing pressolution and cementation but buried dolomitization plays a part reaction on filling pore space, which is limited. Two stages of buried dissolution can be recognized. The first stage happened after seepage reflux dolomitization, which is correlated with dissolution by organic acid, and the second happened in deep buried environment, which maybe is correlated with TSR. Buried dissolution just only improves reconstruction of original reservoir space. |
