Research On Hydraulic Fracture Technologies For Development Of Unconventional Formations Of Sudert Region In Hailaer Oilfield

Xinganling sedimentary tuff formations and Budate metamorphic formations with fractures and dissolved pores/caves are the main formations with low pororsity and extra low permeability of Sudert region in Hailaer Oilfield. Only limited oil could be produced by unartificial method. Hydraulic fracturing technology which is potential to stimulate such formations can provide more estimated and recoverable reserves. However, the structure and lithology of the formations are so complexed and unconventional that conventional fracturing technologies are noneffective because it is difficult to forecast and control fracture splitting and extending with large loss of fracturing fluid. As a result, sand plug is encountered at lower proppant concentration, limited stimulation is obtained, only a few wells are stimulated and improved. In this work, researches on effective hydraulic fracture technologies were carried out to improve the hydraulic fracturing effect and stimulate the formation.First, the sediment, structure, formation and lithology characteristic of the formations were investigated, and injection and production capabilities were researched in detail. It is shown that, Xinganling sedimentary tuff formations are sensitive to water and flow rate for their higher contents of montmorillonite and kaolinite. And Budate metamorphic hidden mountain formations are comprised of fractured calcic medium sand rocks, sand rocks with fine feldspathic rock crumbs and carbonate conglomerate rocks. With lower porosity and permeability, higher drainage pressure, medium/large water sensitivity, weak/medium/large flow rate sensitivity were observed in laboratory. Faults are found in both kinds of formations. More fractures, pores and caves are found in Budate formations. Both kinds of formations were tested with much lower oil production and water injection capabilities. There was almost no oil produced from most formations in the test for oil. The oil productivity index and water injectivity index were extra lower.Second, new earth stress models in view of structural and heat stress were established based on the existing earth stress models, and the earth stress profile interpretation software developed with these models. Then the earth stress of some regions were interpreted with the practical well logging data, continuous earth stress profile data, rock mechanic data, column profile chart and layered data obtained. Then longitudinal and tabulate rules of the earth stress were concluded. These technologies and theories are significant for development of Suderte region effectively.Third, based on the achievements of formation lithology and earth stress etc., the earth stress and hydraulic fracture models of Budate were discussed, the splitting and extending guidelines were presented, the splitting models and solving methods were provided furthermore. At the same time, the splitting and extending principles of Xinganling sedimentary tuff formations were investigated. Whereafter, rock mechanic parameters of both kinds of formations were measured. It shows that matrix of Budate formations is compacted and tight. There are developed fractures, pores and caves in it. The earth stress difference is unconspicuous between the formation and up/under isolated layers because its large thickness. As a result, fracturing fluid loss is large, the splitted fracture inclined to extend vertically, fracture with limited width were obtained, the height of fracture was difficult to control, and it is hard to implemented effective hydraulic fracture. It could be improved by means of reducing fracturing fluid loss and optimizing design of the hydraulic fracture execution. It is advised to fracture the formations combined to restrain the unexpected fracture extension, and/or use fluid additives to control fracture height. Xinganling tuff sand formations belong to elastic rigid formations with large clay content. Their fracture splitting and extending principles are similar to the conventional sand formation, but the width of the fracture and sand added is limited for the effective net pressure decrease in the fracture derived from the plasticity and expanding stress of the rocks adsorbing water. Emulsified crosslinking jelly glue fracturing fluids is potential to restrain water adsorption to the rocks, control fracture splitting and extending effectively.Forth, emulsified crosslinking jelly glue fracturing fluid with lower fluid loss was developed to decrease fluid loss in hydraulic fracture of the formation with complex lithology. Its technological and ecnomics feasibilities are evaluated in terms of prescription optimization, performance characterization, principles of decrease in the fluid loss, models of fluid loss and hydraulic fracturing, and so on. It shows that the fracturing fluid has favorable compatibility, emulsion stability, capability to reduce fluid loss, rheological and glue breaking characteristics, sand carrying capability, and lower damage to the formation. The system is applicable to hydraulic fracture of Xinganling tuff sand formations with strong water sensitivity and Budate formation with fractures, dissolved pores and caves. The principles of its decrease in fluid loss are researched in detail, mainly Jamin's effect, high viscosity, inhibition of the adsorption of water to the tuff rock, flow effect of water and oil phases, and filter cake formed the fracturing fluid involved to decrease the fluid loss. The simulation calculation indicated the emulsified crosslinking jelly glue fracturing fluid is significant to improve the fracture geometry.Fifth, optimization and design of the parameters and technics for hydraulic fracturing of Xinganling tuff formations were carried out according to the earth stress and lithology of the formations. The confecting facility and technological process designed. The effective implementing parameters were determined, The field tests were carried out. The field application results were analyzed. At the same time, some methods and technologies are provided to optimize and design hydraulic fracturing implementation and enhance proppant concentration, which include fracture height controlling artificially, operation with different injection rates, testing hydraulic fracture, and earth stress analysis, etc. And field implementing control technologies for Budate formations also provided, then the field application results are introduced. In the end, the commercial effects of the hydraulic fracturing technologies for the complex formations in Sudert region are introduced.Laboratory and field researching results show that the hydraulic fracturing technologies are feasible and practical to develop Xinganling sedimentary tuff formations and Budate metamorphic formations with fractures and dissolved pores/caves in Sudert region. Large ratio of fracturing fluid flowed back to that injected, higher proppant concentration, higher success rate (up to 80% ~90%), and higher input-output ratio (1:5 and 1:8 respectively) were obtained.