Classification And Evaluation Of High-quality Reservoirs In Low Permeability And Ultra-low Permeability Reservoirs

The Chang 6 oil-bearing formation in the Zhangtai water injection area of Qilicun Oilfield belongs to low-porosity and ultra-low-permeability lithologic reservoirs with poor physical properties and strong heterogeneity.At present,the oil well production in the study area is low,the water content is rising,and the development benefit is worse,so the exploration and development process of oil fields are affected.Therefore,it is necessary to carry out detailed geological anatomy of the water injection area,establish a high-quality reservoir identification standard,and recognize the distribution of high-quality reservoirs to provide theoretical guidance for the next exploration and development and comprehensive management of the water injection area.This paper combines the research results of predecessors,based on the establishment of stratigraphic frameworks,and comprehensively utilizes basic geological data,core analysis data,well logging data and production dynamic data to systematic analyze the stratigraphic,lithologic,sedimentary,reservoir characteristics and four-property relationships of reservoir of the study area.,and establish porosity,permeability,and saturation of log interpretation models in paper.Further,high-quality reservoir identification standard is set up to predict the distribution of high-quality reservoirs in the area.The main understandings are as follows:(1)The sedimentary microfacies and core analysis data show that the Chang 6 oil-bearing formation in the Zhangtai injection area is a delta deposit,of which the Chang 6~1 is the delta plain subfacies,the Chang 6~2,the Chang 6~3,and the Chang 6~4 is the delta front subfacies,but the front delta subfacies is not developing;The rock type is mainly gray and light gray fine-grained feldspar sandstone,the highest feldspar content,followed by quartz and cuttings;the pore type is mainly composed of feldspar,turbidite dissolution pores and feldspar intragranular dissolved pores.(2)Based on the study of reservoir“four-property”relationship,by analyzing the response of various factors affecting permeability in logging data,we choose the relative value of natural potential(?SP)which reflex seepage capability,the natural gamma relative(?GR)which reflect lithology and Vsh and the acoustic time difference(?t)which report size of porosity to set up the multiple linear regression logging interpretation model according to formula.The prediction results are well correlated with the core analysis permeability.The method considers the influence of multiple factors such as porosity and permeability,so the prediction accuracy is higher.(3)High-quality reservoir identification and distribution prediction is the basis of dessert evaluation and the key to increasing reserves and production.Considering the core coring and the limited test data,the prediction of high-quality reservoirs is based on the macroscopic performance of reservoir micro-features,combined with reservoir porosity characteristics,and takes the reservoir thickness,permeability,stratigraphic coefficient(h×k)and the energy storage coefficient(h×?×So)as the main parameters for the evaluation of high-quality reservoirs,and we classify high quality reservoirs in the study area into Class I and Class II.Because single-parameter evaluation often has certain limitations,so in the actual evaluation process,following the multi-parameter comprehensive evaluation principle,high-quality reservoir distribution prediction is carried out for each stratigraphic in the study area,and the high-quality reservoir flat exhibition is verified according to the actual production situation of the oil field.The analysis results show that the wells with higher oil are distributed in the high-quality reservoir development area.