| It has past nearly eight years since the first pilot test phase with the implementation of SAGD in mid-deep strata extra-heavy oil of Du 84 block,the SAGD production obtains a nice effect,it reversed the decline of production.But with the the implementation scale is amplify,many problems are also increased in the production process gradually and the production workload is more and more big,it brings the dynamic regulation some difficulty to control.In order to promote the recovery effect and economic benefit,according to the problems exsit during the SAGD production dynamic regulation process,we carry out research on production law and reservoir engineering optimization of SAGD in mid-deep extra-heavy oil block of Du 84 block on the basic of previous researches in this paper.In this paper,make a stage division of vertical-horizontal wells SAGD and dual horizontal well SAGD's production stage based on analyzing the geological characteristics and production low of Xing?group reservoir and Guantao group reservoir.The production stage of vertical-horizontal well SAGD can be divided into increasing stage,stable stage and decline stage.The stage of dual horizontal wells both can be divided into the stage of production rise sharply,the stage of production is stable and the decline stage of production under the condition of whether there has top water or not in the reservoir.On the basis of stage division,establish production prediction model of different production stage,after simplifying the model of vertical-horizontal wells,the distence from two steam injection vertical wells adjacent on the single part of horizontal production to the horizontal well can be seem as a small dual horizontal wells group,the horizontal production well of dual horizontal well group can be simplified for N samll horizontal wells which length is Li(the plane distance between vertical well and horizontal steam injection well).of small horizontal Wells,horizontal Wells in vertical Wells is establish the model of drainage rate of vertical-horizontal well SAGD duaring the production stage and stable stage.The production forecasting model of vertical-horizontal well SAGD can match with the actual production well,and can be used to guide the practice.Make a further study of Xing?group and Guantao group SAGD's production characteristic curve,then put forward the method of three parameters injection-production curve.It is in good agreement with actual production by using the production model of dual horizontal well and vertical-horizontal well which are established in this paper,and it can be used to guide the production practice.The indicts such as annual production,water content,et al which are predicted by using the dynamic prediction method of SAGD's decline stage can make a good agreement with numerical simulation,and the error is smaller.This method overcomes the limitations of conventional decline prediction of injection-production curve,and can predict the relationship between water content and oil production,the relation between water content and time,cumulative oil production,et al.According to the principle of similarity criterion and the physical simulation,carry out two-dimensional physical simulation experiment of dual horizontal well SAGD and three-dimensional physical simulation experiment of vertical-horizontal well SAGD to simulate the steam chamber's development law,and simulate the steam chamber's development during production increasing stage,stable stage and decline stage.The theory production's prediction models of production increasing stage,stable stage and decline stage which are established by this paper are verified,and make a summary of SAGD's development mechanism from the aspect of steam chamber's development law and the dynamic production et al.By determining injecting steam dryness and calculating of the steam injection volume,determine the steam injection velocity of single well is 90 t/d during the preheat phase of dual horizontal well SAGD,preheating time is 4~5 months,single well's steam injection volume is about 10800~13500 t.The distribution form of steam injection tubing string of horizontal well upside setted down to 2/3 that can make the whole preheating effect of the horizontal section better,and the overall temperature distribution is more uniform.The operation parameters of dual horizontal well's circulation preheat phase were optimized,the operation parameters of uniform pressure cycle phase such as:60~70 t/d steam injection rate;Steam quality of bottom hole>75%;Operating pressure is 4.0~5.0 MPa;Uniform pressure cycle time is 80~90 d;Circulation preheating time of balanced pressure stage:The crude oil viscosity is less than 1000 MPa between the injection-production well.Steam injection rate is 60~80t/d;Bottom hole steam quality is more than 75%;Operating pressure is 4.5~5.0MPa;Equalization charging time:40~50 d.Dynamic parameters is optimized for dual horizontal well SAGD production stage:Steam injection velocity is 275~275 m~3/d.Production-injection ratio is 1.2;Steam quality is more than 75%;Gas injection pressure of wellhead is 4 MPa,Sub-cool value is from 5?to 10?,it can obtain good effect of SAGD's development.Interlayer's length is more longer,width is more wider and the distance from the top is more smaller,the greater influence of interlayer to the steam chamber's development of vertical horizontal well combination SAGD is.When interlayer has incomplete block effect,reflects the mining mechanism that gravity drainage is priority and steam displacement is complementary;When interlayer has completely block effect,embodies double recovery mechanism of steam displacement and gravity drainage.If there are discontinuous interlayers in the design of perforation phase,the interlayers should be perforated upper and lower;If continuous interlayer exsit in the position of 10~15 m apart from the horizontal well above,in addition to perforating performation phase designed under the interlayers,it should also perforate 3~5 m of well phase above the interlayers.The vertical-horizontal well SAGD's concept model of Xing?groups reservoir is established to analyze the influence of injection-production parameters of SAGD stage.When steam injection rate control in 275 m~3/d~325 m~3/d,production-injection ratio is 1.2,steam injection pressure is 4 MPa,the dryness of steam injection is more than 0.75,vertical-horizontal wells SAGD in the reservoir which contained interlayer can guarantee a good development effect.Under the condition of that:steam injection volume is 300 m~3/d,steam injection dryness is 75%,Sub-cool value is 10?,the best time of injection-production parameters operation is that from stable stage to decline stage. |
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