A Case Study Of Subtle Traps From Huanghua Depression

This thesis includes the investigation of subtle trap of hydrocarbon, its classification and state of the art, summarizing the reservoir-forming conditions, types and hydrocarbon distribution of subtle traps in Huanghua Depression. The author put forward exploration methods for subtle traps, and its application is very effective. Combining subtle trap theory with its exploration methods and technology, we have discovered several subtle traps with commercial value in our fields, which leads to the prosperity of subtle trap exploration. This indicates that there is bigger exploration potential in Huanghua Depression. The main achievements as follow:Through extensive investigation, we divide subtle trap reservoir into three types, they are structural subtle trap, non-structural and complex, respectively. Among these, structural subtle trap falls into low relief and little block reservoirs. Non-structural subtle trap falls into unconformity, lithology, water-driving and flaser reservoirs. Unconformity subtle trap further falls into strata-overlapping, strata-unconformity and strata-unconformity basement reservoirs. Lithology subtle trap further falls into updip die-out, paleo-riverway sandstone, lenticular litholgy, bioherm, diagenetic capillary-blocked reservoirs. Complex subtle trap further falls into structural lithology, structural unconformity and lithology unconformity reservoirs. So far, the main theories to study subtle trap include early seismic stratigraphy and late sequence stratigraphy, between them sequence stratigraphy is most effective, its stand tract concepts for different depositional systems is of important significance. By now international exploration for subtle trap is mainly used with paleogeography, which integrates geology, geophysics, geochemistry and drilling, among them, seismic method is getting more and more important.There are a couple of favorable conditions to form subtle trap reservoirs, which are dustpan structure, coexisted slope and sag framework, etc. they lead to form multiple and extensive non-structural traps. The cycles of basin evolution lead to form multiple assemblages of source, reservoir and seal. Qikou, Banqiao and Cangdong source rocks are the building blocks for subtle traps that are discovered in Huanghua Depression, including unconformity, paleo-riverway sandstone, lenticular lithology, strata-unconformity, diagenetic, subtle structural and complex reservoirs. Their distribution of deposition control lithology subtle trap, die-out around paleo-uplift the distribution of subtle traps in the slope, subtle trap forms along faults and above and beneath unconformity boundary.Through exploring and studying in Huanghua Depression many years, we gradually summarize a series of methods and technologies for subtle trap exploration, they are precise stratigraphy correlation on the basis of sequence stratigraphy, including micromarker correlation, element logging, high frequent cycle stratigraphy and precise sequence stratigraphy, besides conventional biography stratigraphy, logging correlation. Through using facies analysis method , the type and distribution of reservoir are determined. Through using microfacies analysis and heavy mineral,the source direction is determined. Through logging facies and sand body contour, the depositional system is determined. Through using wave-classification, stratimagic facies analysis, the reservoir distribution is predicted in the unknown fields. In the favorable targets, we performed precise reservoir prediction, imported and developed high resolution acquisition and processing, polar identification, normal modeling, attribute optimism and prediction, 3-D visualization logging constraint inversion, and predicted the distribution of reservoir.Through the application of theory and technology, we have got the better achievements, especially in the regions of Qikou slope, Bannan slope exploration. Realized the breakthrough of subtle trap reservoirs more than ten years, and discovered, a couple of favorable targets, showed the...