Remaining Oil Distribution Laws Of Ordovician Carbonate Rock Reservoir In Block 2 Of Tahe Oilfield

Ordovician carbonate reservoirs in Tahe Oilfield belong to palaeokarst fracture-cavity type,which are different from fractured carbonate reservoirs or conventional sandstone and carbonate reservoirs.Complexity and particularity of the reservoir are the most prominent feature of this type of reservoirs.The reservoir spaces includes sizable dissolution cave and pore and fracture,which led diverse types and strong heterogeneity of the Ordovician reservoir.Remaining oil distribution is seriously controlled by the type and distribution of reservoirs.The diversity and heterogeneity of the reservoir led to the complexity of remaining oil distribution and large differences in productivity,which have brought great challenges to the development of an oil field.Therefore,this article chose the block 2 of Tahe Oilfield as the study area,explore the remaining oil distribution pattern based on the type of reservoir using the method of combination of static and dynamic with the geological,well-logging,seismic,and development of dynamic data,and reveal the distribution of the remaining oil.Then different potential tapping countermeasures are proposed for enhancing oil rate.The paper made the following main conclusions:(1)Three reservoir types are developed of Ordovician carbonate reservoirs in block 2 of Tahe Oilfield,which are karst conduit type,unaka controlled type,fracture controlled type.And the karst conduit type of reservoir has the best connectivity.(2)Three types and nine sub-types of remaining oil distribution patterns are put forward based on the Ordovician reservoir types in block 2 of Tahe Oilfield,i.e.,karst conduit type,unaka controlled type,fracture controlled type.Karst conduit type includes six sub-types,which are tributary conduit type,conduit terminal type,conduit local high position type,conduit inner sidewall type,pore-fracture type near the conduit,and dense barrier occlusion type.Unaka controlled type includes two sub-types,which are attic dominated type and low-amplitude unaka controlled type.And fracture controlled type just includes pore-fracture type near the fracture.(3)Revealed the distribution of the different types of remaining oil in block 2 of Tahe Oilfield.Karst conduit type of remaining oil is mainly in the erosion area in the north of the Upper Ordovician,mainly include the conduit inner sidewall type and the pore-fracture type near the conduit.Fracture controlled type of remaining oil is mainly in fault-karst reservoir with no well,which is mainly in the erosion area in the south of the Upper Ordovician.And unaka controlled type of remaining oil is distributed within the scope of the study area,which is more in the north area than the south area.(4)Potential tapping countermeasures are proposed for different types of remaining oil distribution patterns,which are new well encryption,acid fracturing,drainage process for oil recovery,improving fluid production,drilling cement plug,water injection,single well gas injection,and unit gas injection.These potential tapping countermeasures can provide some references for oil development program adjustment in block 2 of Tahe Oilfield.