Research On The Logging Evaluation Methods Of Reef Flat Facies Reservoir

Complex sedimentary types and variational lithology and pore spaces are the significant characteristics of reef flat facies reservoir in Longgang area, which caused severe heterogeneity property of reservoirs and difficulty in the logging evaluation. To systemically evaluate and form a set of logging evaluation methods suited for the region, on the basis of analysis properties of different microfacies, this paper establish the logging identification pattern of microfacies, carry out reservoir parameters model and fluid type recognition, together with logging and coring data.Longgang reef flat facies developed three microfacies including platform edge shoal, restricted platform shoal and bioherm. Reservoir characteristics and 4-property relationship are studied. It indicates the sedimentary microfacies corresponds the lithology well. The property of platform edge shoal is better than that of restricted platform shoal and bioherm,but all of them are low porosity and low permeability. The restricted platform shoal includes tight type and fracture-pore type.And bioherm is mainly fracture-pore type. Reservoir in edge shoal is pore type.The pore structure of reservoir are classified The results reveal that the dominant pore structures are I and II types in shoal facies, characterized by large pores and throats. The types of pore structures in bioherm are III and IV, characterized by fine pore and microscopic throat. The favorable reservoir facies belts not only depends on microfacies, but also lies on the development of development of fracture and solution pore.This article identify the sedimentary microfacies using well logging data by combining the discriminant analysis of the attribute parameter of different microfacies, which relies on the rock physics domain distribution of microfacies, and the analysis based on the well logging curves, which relies on the macro morphologic change of the microfacies. On this basis we establish the well logging identification pattern of the microfacies in the research area by utilizing FMI. The platform edge shoal shows a “ three low” feature in conventional well logging, wavelet coefficient of the curve have a range from 0.05 to 0.15, FMI shows block structure. The bioherm shows feature of low gamma in conventional well logging, wavelet coefficient of box-like curve is less than 0.05, FMI shows a densification and high resistance pattern. The intertidal flat shows feature of high gamma and low electrical resistivity in conventional well logging, wavelet coefficient of dentation curve have is larger than 0.15, FMI shows stripped pattern.In view of the characteristics that reef flat facies reservoir developed both pore and fracture, the porosity calculation models of different microfacies are established through core calibration logging method, together with dual-lateral log numerical simulation and FMI. The permeability calculation models are established through flow unit index method to improve calculating precision.Based on the fluid type analysis through resistivity method, P1/2 judging method, overlapping method and using information of P-wave velocity and S-wave velocity, The standard for fluid identification is established on the basis of microfacies. The optimized method for applicability is selected for the pore type reservoir of platform edge shoal in feixianguan formation and the pore-fracture type reservoir of bioherm in Changxing formation.