Marine carbonate reservoir characteristics of the Middle Ordovician Majiagou Formation in Ordos Basin
Wang Qicong1, Zhao Shuping1, Wei Qinlian1, Xiao Ling1, Yang Yihua2, Guo Yanqin1, Niu Miaoning1
1 School of Petroleum Resources，Xi′an Shiyou University，Xi′an 710065，Shaanxi 2 Institute of Petroleum Exploration and Development, Changqing Oilfield Company, PetroChina, Xi′an 710021, Shaanxi
Abstract：This article discusses the petrophysical facies characteristics of the Majiagou Formation marine carbonate reservoirs and the method of carbonate reservoir classification in the Ordos Basin.On the basis of outcrops，cores，and slices analysis，combining with reservoir physical property and pressured-mercury testing，the rock types，porosity texture，and physical property of carbonate reservoir were studied.Using flow zone index FZI，the authors studied petrophysical facies characteristics and the classification of carbonate rock reservoir.There are 8 types of carbonate rock reservoir in the Majiagou Formation including dolomitic solution-collapse breccia，dissolved anhydrite or salt dolomitic breccia，containing anhydrite or salt dolostone，anhydrite or salt dolostone，aplite dolostone，residual structure fine-coarse crystalline dolostone，secondary limestone and micritic limestones or putty crystal dolostone.There are 4 types of storage space founded in the Majiagou Formation carbonate rock reservoir including karst cave(＞100mm)，dissolved pore(2～100mm)，pore(＜2mm)and fissure.There are 4 kinds of storage and seepage of reservoir including pore reservoirs，fractured reservoirs，fractured porous reservoirs，and fractured porous and vuggy reservoirs.According to flow zone index FZI reservoirs are divided into 6 types of petrophysical facies and 24 subfacies.Carbonate rock reservoirs are divided into 5 types and 7 subtypes.Type Ⅰ reservoirs are the best type of gas storage plays mainly distributing in the M15，M45 and M65.Type Ⅱ and Type Ⅲ reservoirs are main reservoirs in the Majiagou Formation.Subtype Ⅱ1 and Ⅲ1 reservoirs primarily containing pore mainly distributed in the M15-M65 and subtype Ⅱ2 and Ⅲ2 reservoirs primarily containing fracture mainly distributed in M4.Type Ⅳ reservoirs are of poor physical properties and distributed in all formation.Type Ⅴ reservoirs are non-reservoirs.Study results show that the method on the basis of petrophysical facies research is an effective way to reveal carbonate rock reservoir characteristics and carry out quantitative classification and evaluation of carbonate rock reservoirs.
Wang Qicong,Zhao Shuping,Wei Qinlian et al. Marine carbonate reservoir characteristics of the Middle Ordovician Majiagou Formation in Ordos Basin[J]. JOPC, 2012, 14(2): 229-242.
