Optimization Of Fracturing Fluid System In Dolomitic Claystone Reservoir With Acid Sensitivity In Baiyinchagan Depression

The structure of dolomitic mudstone reservoir of Baiyinchagan depression is complex.Nowadays,the research of reservoir characteristics is not enough.The fracturing fluid in view of this reservoir is bad.For the dolomitic mudstone reservoir in Xi 26 block,the geology,lithologic characteristics,reservoir space,physical property characteristics and reservoir characteristics were studied,the velocity sensitivity experiment,water sensitivity experiment,acid sensitivity experiment,alkali sensitivity experiment,acid dissolution experiment and expansion experiment were implement,optimizing the thickener,clay stabilizers and surfactants,forming the fracturing fluid formula,analyzing the compatibility and performance evaluation.Studies had shown that,in Xi 26 block’s dolomitic mudstone reservoir of Baiyinchagan depression,rock’s types were special,rock mineral composition was complex,reservoir was very hard and brittle,the holes and cracks were a lot,the substrate had low permeability,and the reservoir had high acid sensitivity,low alkali sensitivity,low water sensitivity and no velocity sensitivity.Rock acid dissolution rate was 41.8~55.7%,considering rock reacting with hydrochloric of more than 6% concentration would produce silica gel,so the reservoir was inappropriate to acid fracture.Core inflation rate was 2.44~2.44%,then it was decided hydraulic fracturing method should be adopted,in dolomitic mudstone reservoir of Baiyinchagan depression.Modified guanidine gum B as thickener,WD–10 as clay stabilizer and SP–3 as surfactants were optimized.Optimum formula was 0.3~0.4% concentration of guanidine gum base + 0.5~1.0% concentration of clay stabilizer + 0.2~0.5% concentration of surfactant.For the low damage fracturing fluid,its viscosity met the construction requirements,residue content was up to standard,broken gel is complete,degree of core damage was low.For the field application of 13 wells 15 times,the well construction success rate was 86.67%.Oil Wells after fracturing optimization increased 7490.4t oil,added fluid 20930.4 m3.Economically,input and output was 1:6.08,it obtained the good economic benefits.It achieved the effective use of the dolomitic mudstone reservoir of Baiyinchagan depression.And it provided technical support for exploration and development of this kind of reservoir.