Reservoir Parameters Estimation with Some Log Curves of Qiongdongnan Basin Based on LS-SVM Method

Reservoir porosity and permeability are considered as very important parameters in characterizing oil and gas reservoirs. Traditional methods for porosity and permeability prediction are well log and core data analysis to get some regression empirical formulas. However, because of strong non-linear relationship between well log data and core data such as porosity and permeability, usual statistical regression methods are not completely able to provide meaningful estimate results. It is very difficult to measure fine scale porosity and permeability parameters of the reservoir. In this paper, the least square support vector machine (LS-SVM) method is applied to the parameters estimation with well log and core data of Qiongdongnan basin reservoirs. With the log and core exploration data of Qiongdongnan basin, the approach and prediction models of porosity and permeability are constructed and applied. There are several type of log data for the determination of porosity and permeability. These parameters are related with the selected log data. However, a precise analysis and determine of parameters require a combinatorial selection method for different type data. Some curves such as RHOB,CALI,POTA,THOR,GR are selected from all obtained logging curves of a Qiongdongnan basin well to predict porosity. At last we give some permeability prediction results based on LS-SVM method. High precision practice results illustrate the efficiency of LS-SVM method for practical reservoir parameter estimation problems.

Focused Fluid Flow, Shallow Gas Hydrate, and Cold Seep in the Qiongdongnan Basin, Northwestern South China Sea

The 3D seismic data acquired in the central Qiongdongnan Basin, northwestern South China Sea, reveal the presence of shallow gas hydrate, free gas, and focused fluid flow in the study area, which are indicated by multiple seismic anomalies, including bottom simulating reflectors, polarity reverses, pulldowns, minor faults, and gas chimneys intensively emplaced within the shallow strata. A new cold seep is also discovered at approximately 1520 m water depths with an ~40 m wide crater in the west part of the study area. Water column imaging, seafloor observation, and sampling using the remotely operated vehicle “Haima” demonstrate ongoing gas seepages and shallow gas hydrates at this site. Thermogenic gas in the study area migrates from the deep reservoir through the gas hydrate stability zone along deep faults and gas chimneys, forms shallow gas hydrate and free gas, and sustains localized gas seepage within this cold seep. The results provide insight into the relationship between shallow gas hydrate accumulation and deep hydrocarbon generation and migration and simultaneously have important implications for hydrocarbon explorations in the Qiongdongnan Basin, northwestern South China Sea.