Comprehensive Evaluation Of Chang4+5 Reservoir Of The Yan Chang Formation In Zhang Xiliang Oil Region

Enhancing exploration and development, improving oil recovery and increasing recoverable reserves of low permeability and porosity reservoir, which is one of the focuses of current oil and gas exploratory development. Zhang Xiliang region is located in the west of Shanbei slope of Ordos Basin. Chang 4+5 group is one of the main oil reservoir in the area, and features a complex reservoir geology and strong heterogeneity, which limits development later stage of the reservoir. In this background, by using of drilling, mudlog, coring, welllog, testing, various analysis data, and based on sequence stratigraphy, reservoir sedimentology, petroleum geology, logging geology, etc, do some research in sedimentation, diagenesis type, pore structure characteristics, reservoir physical property and oil content of Chang 4+5 group. Building reservoir classification evaluation criteria and give a comprehensive evaluation standard of reservoir, find favorable area with relatively high porosity and permeability in the low permeability and porosity reservoir.The research shows that Chang 4+5 reservoirs have a stable structure, and regional structure is west-dipping monoclinic, part of region raise small nose uplift; Depositional environment is delta front sedimentary, sand body is developed, sedimentary microfacies is underwater distributary channel, underwater distributary bay, mouth bar and sheet sand; Diagenesis reservoir rock types are mainly compaction, cementation and dissolution, which feldspar dissolution improve reservoir property largely; The analysis of reservoir physical property characteristics indicates that Chang 4+5 group is typical low permeability and porosity reservoir with strong heterogeneity. By making use of logging technology, some research for the "four characteristics "relationship of reservoir shows that low resistivity oil layer and high resistance water layer are distributed in Zhang Xiliang region. Through a single well overlays and multi-well cross plot technique, these unconventional oil layer can effectively identify, meanwhile according to Archie, establish quantitative interpretation of reservoir oil model to the high-pressure mercury and oil-water relative permeability curves for its check and found high precision.Ultimately, the evaluation standard of reservoir classification is established by choosing multiple parameters to comprehensively evaluate for Chang 4+5 reservoir in Zhang Xiliang region, which is classified by class ⅠI, Ⅱ, Ⅲ Ⅳ, Class Ⅰ, Ⅱ, Ⅲ as effective reservoir has a certain adsorption and transfusion capability of oil, gas and water reservoir, and class Ⅳ is almost invalid reservoirs.