Analysis Of Xiashihezi Ⅲ Gas Reservoir Permeability Changes After Fracturingin Daniudi Gas Field

Daniudi gas field he3gas reservoir is a lithologic gas reservoir in the lowamplitude structure. Its reservoir with the characteristic of poor reservoir physicalproperty which represents in low porosity and permeability, and strong heterogeneity inboth vertical and horizontal，the basic characteristics of natural capacity etc. During thegas well before fracturing the end improves the situation of relatively poor reservoirdamage is more serious. Daniudi gas field wells rely on fracturing in order to obtainindustrial gasflow.In accordance with Daniudi gas field reservoir characteristics and relations, on thebasis of previous research, combined with low-permeability oil field evaluation methodto determine the lithology, physical properties, pore structure, the gas-potential andelectrical parameters for reservoir analysis and evaluation methods. The district’sreservoir is divided into four types, namely Ⅰ type reserviors and Ⅲ type reservior, ⅢItype reservior, Ⅳ type reservior, representing a good reservoir, secondary reservoir,poor reservoir and non reservoir. he3gas reservoir of the northern which are mainly ⅢItype reservior,followed by I type reserviors and Ⅱ type reservior, Ⅰ type reserviors andⅡ type reservior are mainly to the south, Ⅲtype reservior and Ⅳ typereserviordistribution is limited.According to report data of the currently existing geological and over the years putinto the gas production test, comparing the results obtained by the DST test resultsachieved with pressure recovery test relative, and capacity of the reservoir seepage andproductivity can been significantly improved after Daniudi gas field he3gas reservoirfracturing. According to the revisions analysis results of modified isochronal test andsingle point test get forecast fractured the relation of open-flow capacity QAOFandformation conductivity kh: QAOF=6.1968（kh）0.9355. It is known that after fracturingopen-flow capacity can obtain the effective permeability after fracturing. Based on dataof logging, core and well test report,we can obtain the effective permeability beforefracturing, and then compare the effective permeability after fracturing significantlygreater with the effective permeability before fracturing, range from2to30times. Inthe same gas reservoir permeability changes before and after fracturing of the range isvery large, this is the reservoir geological factors and engineering factors common decision.Pressure recovery not entirely the case, according to the well test interpretation oftheoretical plates and the characteristics of low permeability fractured reservoirs, andfor Daniudi gas field geological studies, well test data, the characteristics of test gas andproduction material reflection, through the Daniudi gas field well test model, andexplain the reservoir parameters.After fracturing, reservoir seepage condition isimproved, productivity is increased substantially. According to the Daniudi gas field thesingle well productivity classification standards, for Daniudi gas field he3reservoirproduction wells are classified.175single production wells exist in the gas reservoir,21high output wells,70middle output wells, and84low output wells. According to thesingle well water production and stable classification criteria of Daniudi gas field he3reservoir production wells are classified, and the results show that are all wells of thegas reservoir are low water output wells, including96stable wells,79non stable wells.Daniudi gas field belongs to the low permeability compact gas field, basically fracturingput into operation, and rely on fracturing to obtain commercial gasflow. According tothe actual open-flow potential and develop dynamic, formation coefficient to capacity,the impact of the productivity prediction equations QAOF=6.1968（kh）0.9355, theformation coefficient is greater, the capacity is greater.In the main controlling factors of the property, sedimentary microfacies control thephysical property of the macro distribution, the main channel property is the best,channel edge is the second smallest, and worst flood plains; He3gas reservoir of sandbelongs to the development of sintan formation, the grain size of rock give first place tothe coarse-grained and mesograin, lithology give first place tolithic sandstone, lithicquartz sandstone and quartz sandstone lithology, main hole throats value, good physicalproperties; lithologic directly influence the quality of the physical properties, generalcoarse grain class above the sandstone sandstone property is generally good, and withthe increase of the content of quartz, property is betterobviously, can form goodproperty condition; the pore structure is from the microscopic affects reservoir seepageability, thus affect the production capacity of the gas reservoir. The reservoirheterogeneity and high output of a layer distribution has the close relation, researchshows that, the high outputing wells main appearreservoir area where I type reservoirdevelop, Ⅱ type reservoir and Ⅲtype reservoir develop middle-low output well, IV typereservoir does not exist capacitybasically; and (including gravel) thick sandstone abovelevel of the lithology, high output well is more; the grade difference of porosity ofpermeability are bigger,the heterogeneity degree is higher, productivity is higher.Theinfluence of gas well productivity for testing time is particularly important, onlystability test time to a certain after, get gas well productivity is more accurate.The scaleof add sand amount between40m~3and70m~3,the vast majority of the well for middleoutput well, the scale of add sand amount between70m~3and120m~3for high output wellcommonly. Improve the efficiency of return discharge, help to improve the productivity of the gas well fracturing.Fracturing crack are more long, the bottom of the seepage toimprove the ability, the discharge area of well are more, the fracturing well after layersof open-flow capacity increase are more obvious. Fracture height control to crack in thegas pressure in fully extended, and the reasonable selection of selecting well layer andfracturing way, thus can increase production capacity.Combined with Daniudi gas field he3reservoir, and influence factors ofcombination of fracturing and layer selection basis: Well as far as possible in the centerof chanle choice, and the chanle concave bank, chanle fork or collection in the near ofthe major line, followed by chanle overflow flanks and even to shore; Reservoir typesfor Ⅰ type and Ⅱ type reservoir, rock lithology of sandstone, thick sandstone for particlesize, quartz content is higher, the median radius is bigger, the reservoir heterogeneity isstrong horizon. After fracturing the height of the crack is less than the thickness of thecompartment, but also try to make the pressure cracks in the radial extension is longer,larger scale of fracturing way to put into operation. When gas well is fracturedthe scaleof add sand amount between70m~3and120m~3, and improve rateof fracturing fluid returndischarge.