Research Of Glutenite Reservoir Characters, Classification And Evaluation Of Qie12 Area In Kunbei Oilfield Of Lower Ganchaigou Formation In Qaidam Basin

Sandy conglomerate is widely distributed in China,with the attributes such as near provenance,large thickness,quick phase transition.Besides,it is difficult to make reservoir subdivision,correctly identify the underneath fluid or to distinguish good and bad reservoirs,due to its strong anisotropy,complex mode pore-throat structure,low calculating precision for parameter.By taking the example of the lower segment of Ganchaigou formation(E3’),Qie-12 well of Kunbei oilfield in Qaidam Basin,Qinghai Province,this thesis has developed a set of methods to subdivide thick sandy-conglomerate reservoirs in fan delta facies,figure out the characteristics of the reservoir,control factors and classification methods,and improve physical interpretation accuracy of sand-conglomerate reservoirs and fluid identification conformity.(1).The thesis has formed a set of research methods to subdivide sandy-conglomerate reservoirs.First,use the core analysis and electro-imaging data to establish a complete rock sedimentary unit of time sequence and the contact characteristics of different depositional time unit.By comparing the two sets of data, figure out methods to subdivide neutron- and sound-wave curve calibration method and neutron-wave wavelet analysis method in conventional logging,three depositional time unites divided in target exploration zone, and realize full-region closed comparison.(2).The provenance of the research reservoir is located in Aral water system to the west of the Qaidam Basin,and mainly develops into two sub-facies of braided river delta plain and delta front.The major micro-facies are water distributary channel,underwater distributary channel and mouth bar.(3).Through the "four-character relationship" analysis,the thesis combined the dynamic production data,determined the quantitative identification standard,formed a rapid methods to identify oil and gas by hydrocarbon value and established model for physical parameter interpretation in accordance with production performance by segmentation(hole enlargement section and non-hole enlargement section)and different lithologies(sandstone and conglomerate).(4).The main lithologies of the reservoir in this study are sandy conglomerate and sandstone,with an average reservoir porosity of 10.5% and permeability of 3.8 mD,making it classified as a low porosity and permeability reservoir.The physical property would mainly turn good as clay content and size get smaller(sandstone is more sensitive to this factor).Sorting has a second important influence on reservoir’s physical properties and carbonate content the least.Quality factor and mercury intrusion pore-structure parameters of the selected reservoir have divided the reservoir into four categories,including Ⅰ-class reservoir with RQI factor bigger than 1.2, displacement pressure less than 0.2 MPa,porosity bigger than 13%,permeability bigger than 15 mD,oil content(oil-immersion level)of 3%;Ⅱ-class reservoir with RQI factor betweenl.2 and 0.35, displacement pressure between 0.2 and 0.4 MPa,porosity bigger than 10%-13%,permeability bigger than 1 to 15 mD,oil content(oil-patch level)of 8%;Ⅲ-class reservoir with RQI factor between 0.35 and 0.22,displacement pressure between 0.24 and 1.3 MPa, porosity bigger than 10%-8.3%,permeability bigger than 1 to 0.4 mD,oil content(oil-stain to oil-patch level)of 50%;IV-class reservoir with RQI factor less than 0.22,displacement pressure bigger than 1.3 MPa,porosity less than 8.3%,permeability less than 0.4 mD,no show of core.The former three types are mainly types of oil and gas occurrence;effective evaluation with the aid of nuclear magnetic resonance(NMR)and mercury injection has found that,the former three kinds of reservoirs have a porosity of 30 to 35%,mesoporosity of 30 to 40%,with the rest in microporosity.(5).Given that the water content moves upward quickly in Ⅰ, Ⅱ,Ⅲ reservoirs,flat contradiction could be alleviated by cutting down water injection rate.The water wells in Ⅳreservoir acidification could have formation energy complemented through acidification and boosting water injection,while the oil wells inⅣreservoir could raise single well production by reservoir fracturing and perfecting well flood pattern.