The Optimization Research Of Fracture Network System In Tight Oil Reservoir

Tight reservoir has the features of ultra-low permeability and well-developed naturalfracture, stimulation effect is always unsatisfactory by conventional fracturing of singlefracture. Horizontal well volume fracturing adopts the technology of multi-stage andmulti-cluster and reorientation material, develops complicate network that main fracture andbranches interact with each other which enlarges the stimulated reservoir volume and it isbecoming a new fracturing technology in the tight reservoir development. There are nothoroughly researches on best fracture network, formation energy supplement and networkparameters optimization of the early stage of the tight reservoir development. Therefore, thispaper firstly generalized the reservoir conditions needed to develop complicate network inhorizontal well volume fracturing and the fracture network form after the treatment of volumefracturing, built simulation methods of complicate fracture network system and networkparameters of volume fracturing in tight reservoir, and then built production prediction ofmulti-stage and multi-cluster fracturing based on the tri-linear flow model proposed by Leeand Brockenbrough to study the fracture distribution of multi-stage and multi-cluster fracturesof horizontal well and analyze the influence of fracture distribution on post fracture response.Sensitivity analysis on network parameters was proceeded by means of Plackett-Burman testanalysis method, based on this, oil drainage characteristics of different network forms underdepleted development were studied using numerical simulation technology and reasonablenetwork forms and injection/production patterns are determined, and then influence ofnetwork parameters on development effect was studied aimed at optimized network condition.Results show that, influence of different fracture distribution patterns on production aftervolume fracturing is great, two of the most important control factors are drainage area of theheel fracture and interference of the inner fractures; sensitivity degree of the networkparameters: semi-stripe length>main fracture flow conductivity>secondary fracturespace>bandwidth>cluster space>secondary fracture flow conductivity; In the light of the12different network forms designed in this paper, fusiform and dumbbell form fracture networkall show obvious advantage whether the cluster is big or small, and their development effectare better than inverse triangle and rectangle network form; when cluster is different and stimulated reservoir volume is same, the longer the stripe length, the stronger ability tocommunicate the farther reservoir away from the wellbore is. the optimum parameters of thefracture network for seven-spot well pattern are: stimulated reservoir volume964.8×104m3,stimulated reservoir area32.16×104m2, semi-strip length340m-380m， main fractureconductivity300×10-3μm2·m, band width60m-80m, second fracture conductivity20×10-3μm2·m. The researching results provide theoretical base for volume fracturing designof the tight reservoir.