Evaluation Of Water Injection Development In Tahe6-7of Fractured-vuggy Carbonate Reservoir

For carbonate reservoir exploration and development, high heterogeneity ofreservoir is very prominent problem. Especially when the reservoir mainly consists offracture and vuggy, it is complex for the judgment and cognition of reservoircharacteristics. Fractured-vuggy carbonate reservoir is of high heterogeneity, and thevariying structure of reservoir, confusion relation between oil and water makes manyexisting theoretical knowledge and practical experience of clastic reservoirs cannot beapplied. Fractured-vuggy carbonate reservoirs are difficult to develop reservoir atdomestic and abroad. The reservoir development theory and practice are at theexploratory stage. Although researchers has done a lot of researches, the current levelof cognition is far from meeting the needs of exploration and development in Taheoilfield. Therefore, Studying complex production characteristics of fractured-vuggyreservoir combined with the dynamic production data of carbonate reservoir in Taheoilfield, has great practical significance to formulate development plan in the future.The block6-7of Tahe reservoir is developed with taking fracture-vuggy as thebasic unit, and good results are achieved. With the exploring and developing of oilfield, productivity differences between fracture-vuggy units, the production decline,the changes of water content and other dynamic features, have seriously affected theformulation of development policy and the evaluation of development. Phenomenonof water breakthrough is becoming serious in the injected fracture-vuggy units. As theconnecting mode between fracture and hole is hard to evaluate, the pertinence ofprofile modification is poor, which results in decreasing efficiency of profilemodification. So it is urgent to research and analyze the connecting mode of thefracture-vuggy unit, characteristic and influence factors of water production, waterinjection effects. It is a basic work for analyzing profile modification measurementand improving the development efficiency in the future, also can provide a referencefor the development of similar reservoirs.Based on the static and dynamic data of production, the typical single wellreservoir unit is classified in the Tahe6-7fractured-vuggy reservoir, and theinterference well test, similarity of production feature, analysis of pressure system,effective response for water injection, tracer analysis etc. are used to analyze the connectivity of fracture-vuggy system. According to the static and dynamicproduction data, the water producing characteristics and oil-water distribution areanalyzed. On this basis, the injection-production well groups are divided. Bycomparing the injection effect of single well within group and comparison analysisbetween the injection-production well groups, and four indexes(production declinerate, rate of increase of water, pressure maintenance level, waterflooding curve) thewater injection effect of the typical fracture-vuggy unit has been evaluated. Theresults are as followed:(1) Well drilling reservoir space type determines the communication patterns andrelationship between injection-production and producing wells. Combining theanalysis of static and dynamic data of production, the reservoir types of single well inthis fractured-vuggy reservoir are divided into yuggy type, fracture-vuggy type andfracture type.(2) Combined with static and dynamic data, the interference well testing,similarity of production feature, analysis of pressure system, effective response forwater injection, tracer analysis etc. are used to analyze the connectivity offracture-vuggy system. The results show that, connectivity of wells in onefracture-vuggy unit is good, but there is connectivity among wells from respectivefracture-vuggy unit.(3) The features of water production of single well are divided into4categories(slow increasing, stepwise uptrend, fast rising, wave type). Most of them are fastrising and wave type，while slow increasing wells are the least. Single well producingwater feature is mainly determined by reservoir space types and reservoirdevelopment of the well.(4) The typical oil-water interface of fracture-vuggy unit was evaluated, andoriginal oil-water interface of the typical fracture-vuggy system and its variationcharacteristics were analyzed. Understanding the change of the oil-water interface insingle well or well group provides the basis for the flood control measures.(5) Injection-production well groups are divided by the combination of waterinjection well as center and the production characteristics. The effects of productionwells are evaluated and A well and B well were distinguished according to effectiveresponse from the production well; Here are the comprehensive evaluation on theeffect of injection unit. The analysis shows that S80unit injection effect is good as awhole, while the S67unit injection effect is not satisfied. (6) The analysis of single well water injection effect by relationship betweeninjection-production and producing wells shows: In general, fracture injection-vuggyproduction effect is better than that of vuggy injection-fracture production. The effectof low injection-high production is better than that of high injection-low production.Slow rate of water injection was suggested in fracture injection-fracture productionand water injection rate shoud not be too fast. The overall results of water floodingrule is: reservoir with poor porosity and permeability shoud be of water injection,while the production of reservoir with good porosity and permeability is good.