Fractured Reservoir Evaluation Using 2-D Imaging Logging Data

More attentions should be focused on the fractured reservoirs parameters calculation and logging evaluation, which are an important basis for estimating reserves with the development of world oil and gas industry. Fracture reservoirs pore space is usually divided into threee types: matrix pores, fracture pores and vug pores. All these three kinds of pores space have strong inhomogeneous and anisotropy, so the Archie formula model is no longer applicable for the fractured reservoir. It shows a dramatically increased range of the m, n value in because of the complexity of pore genesis and pore structure in fractured reservoir. In order to realize the logging evaluation of fractured reservoir, we usual need to use the dual-pore structure model or tri-pore structure model to obtain the value of m, and seek a reasonable form of Archie's expansion to improve the calculation of water saturation. In the past, it is difficult to obtain the exactly fracture parameters form the conventional logging, so a lot of influence factors such as fracture dip and fracture tortuosity are not considered into the former pore structure models. A new tri-pore structure model is developed for petrophysical evaluation of naturally fractured reservoirs where dip of fractures ranges between 0 and 90 degrees, and where fracture tortuosity is greater than 1.0. The model leads to the observation that including fracture dip and tortuosity in the petrophysics analysis can generate significant changes in the composite system pore exponent(m). The single influent factor of composite system pore exponent m are studied, such as fracture tortuosity,fracture dip,fracture porosity,matrix poroity and non-connected porosity. Furthermore, logging data from Chegu Area in Shengli Oilfield are reprocessed to improve the saturation evaluation combining with the Archie model. It is concluded that different types of reservoirs (fracture typed,pore typed,fracture and vuggy typed,vug typed)have its own m value range. The result will be helpful to the logging evaluation of fractured and vuggy reservoirs.