The Key Technology And Application Of Openhole Horizontal Well Multi-stage Fracturing Of Tight Sandstone Reservoir

Shengli Oilfield is rich in tight oil reservoir resources.The proved and controlled oil reserve in this reservoir is about 5.59×108t and the prospective reserve is about 6.46×108t.During the 12th 5-year-plan in China,nearly 70%of the newly proved and undeveloped reserves is tight oil in deep reservoir,which makes the reservoir become the major production base for sustainable resource.However,the reservoir formations are characterised by bad physical characteristics,complex lithology,poor separation and connectivity of the porosity,and substantial heterogeneity.Because the drainage volume is small,production decline is fast,and the productivity is very low,it is hard to stimulate oil production efficiently by using conventional verticle fracturing treatment even if improve fracturing scale.To enlarge fracture volume in tight oil reservoir and improve oil production,an open-hole horizontal well multistaged fracturing technology is investigated and developed,in which the fracture propagation description,the productivity model,the fracture parameter optimization,the open hole staged fracturing well completion pipe string,the real-time mixing-preparation fracture fluid,the staged fracturing techniques,and associated in-situ application are the main concerns.With the knowledge of physical model about conventional simple fracture propagation,an integrrating description method for fracture propagation near horizontal wells is developed based on physical model,CT scanned 3-D image,and numerical model technology.By using the proposed method,the morphologic variation of hydraulic fracture propagation near horizontal wells can be described and illustrated stereoscopically and quantitatively.It is firstly found that the controlled reserve can be improved after fracturing operation as long as the similar transection fractures could form within the region between horizontal well bore and initial stress direction.It is the deviatoric magnitude of horizontal major stresses that causes fracture morphyologic variation complexity.This finding is meaningful for the design optimization in drilling and fracturing operations.Considering that the current non-Dacy percolation productivity model,multi-fracture interference model,percolation characteristics of thin interbed after fracturing treatment in horizontal wells in tight oil reservoir still need to be further investigated,the flow filed in matrix,fractures,and wellbore are systematically grouped as three-flow-field.With the knowledge of three-flow-field coupling action,stress sensibility,and strong non-linear percolation of thin interbed reservoir,a non-Dacy percolation model incorporating three-flow-field coupling action is proposed based on potential energy stacking principle and effective recovery theory.The newly proposed model is suitable to horizontal well production of tight oil reservoir in Shengli Oilfield,and meaningful for the further improvement of productivity prediction model about horizontal well fracture.Incorporating the newly proposed model,the productivity prediction is more reasonable and a prediction accuracy of 85%is achieved.A fracture parameter optimiaztion platfrom for long well section in horizontal wells by open hole completion is built up.The gordian technique for the successful multistage fracturing operation in horizontal wells is staged fracturing completion pipe string with open hole packer.Since borehole of open hole completion is irregular,temperature is high,we R&D(reasearch and develop)a kind of dual packing element compression open hole fracturing packer whose temperature tolerance is 150?,resistance to pressure is 70MPa.It can effectively packoff open hole wellbore.To satisfy modifying multistage,high-duty,erosion resistance ball injector sliding sleeve and low density ball are developed.Ballseats' minimum stage different is 3.0mm,and the minimum stage different between ball and ballseat is 2.6mm.It has 15-stage open hole staged fracturing capability.To realize conventional guar modification speed increaser and dispersant are added so that the dissolution speed has improved.The salvation of fast hydrating guar is 86%per minute.For the conventional guar,the preparation process is very difficult,swelling time is long(2-4hrs),it must be prepared ahead of time and need many tanks.The newly developed guar has solved all these issue and satisfy large fluid volume usage in horizontal well staged fracturing and it can be made up real-time in-situ continuously.With the help of fracturing fluid sand-transport physical modeling,full 3-D fracture propagation analytical model,sand input parameters optimization,corollary fracture monitoring technology,the horizontal well multistage modification is realized.This technology is apllied in 24 wells successfully,success ratio 100%,produce 1078×104t oil from compacted sand matrix.The average single well production is 3-5 times higher than that of verticle wells in the same block,solving the issue of recovery from compacted sand matrix in Shengli Oilfield,promoting to produce in dense sandstone reservoir,making further improvement on high efficiency recovery in low permearbility layers in Shengli Oilfield.It has great significant in dense formation recovery.During the research,2 SCI papers,2 EI papers are published,1 paper is published in key periodical.Allthe papers are about fracturing propagation analysis,fracture pressure monitoring technology are published.