Tahe Oilfield Ordovician Complex Carbonate Reservoirs In Log Interpretation And Evaluation Methods

The Tahe oil field is located in the southwest of the Akekule lobe of the Shaya heave, which belongs to the north area of the Talimu basin. It is a large-scale reservoir discovered in recent years with more than 100 million reserves. For the reservoir, the Ordovician carbonate is the main oil-bearing layer that has been proved by years of production. The studied carbonate is mainly composed of limestone with the percentage up to 99%. Peculiarly, the carbonate reserve space is proved to be composed of the complicated pore-fracture-cave system that formed from the tectogenesis and karsification. The pore spaces include matrix pore, fracture and karst cave, of which the matrix pore has low porosity and poor permeability and contribute little to the reservoir, while the fracture and karst cave become the main reserve and permeable spaces and have great effect on the reservoir. It is a great challenge for the well-logging interpreters to evaluate on such reservoir that has complex pore structure and special diagenesis and serious anisotropism of the carbonate itself, especially when there has no image logging data, such as FMI for help, so that it is of important practical value to effectively and timely study and set up one set of conventional logging evaluation technique for such kind of complex carbonate reservoir.The thesis is just from this kind of point of view. It mainly consists of two parts. The first part is of importance, for it will be viewed as the theoretical foundation of the whole work, and the main content includes some basic but key theories related to the complex carbonate reservoir. The theories also include the relations between the carbonate reservoir and the logging response and introduce some achievements and conclusions from the former experts in the logging interpretation filed. At the end of this part some mathematical methods will be introduced, including the regression approach, Shannon entropy, the wavelet neural networks, etc. The second part is the key content of this thesis, which is composed of the 3rd chapter, the 4th chapter, the 5th chapter, the 6th chapter and the 7th chapter. Some basic information related to the studied area will be introduced first. And then combined with the practical conditions of the studied carbonate reservoir, the thesis has analyzed the logging response character of fractures and karst caves, especially the identification of the karst cave reservoir from the conventional logging curves. The complex pore media model has then been set up and used to evaluate the carbonate reservoir, including the reservoir type identification by conventional logging and the reservoir parameters calculation, such as porosity, water saturation and permeability, etc. And the complex pore media model and the parameters calculation models have been applied to the Ordovician carbonate reservoir of the Tahe oil field. Some evaluations related to the carbonate reservoir have been done in the work, including the fracture development degree estimation and the fluid property identification. The thesis has also analyzed and plotted the planar distribution figures of the reservoir parameters and the karst cave reservoir. The detailed description for their vertical and planar distribution character has been given in the thesis. One set of the conventional logging evaluation methods on the complex carbonate reservoir with frature-karst cave has been set up. It is for the Tahe oil field and also can be applied to other areas that has similar kind of reservoir.