Study On Rock Mechanical Characteristics And Volume Fracturing "Sweet Spot" Of Tight Sandstone Reservoir In Area X

Volumetric fracturing technology is an important measure to improve the production of tight oil and gas reservoirs.At present,there were 16 testing wells in X area for volume fracturing in tight sandstone reservoir,but some of them have poor fracturing effect.In order to improve the development efficiency,it is necessary to strengthen the study of reservoir geological characteristics and fracturability,and establish the optimization criteria of volume fracturing geological "sweet spot" and engineering "sweet spot" in area X,so as to select the fracturing interval.This paper selected the Chang 8-Chang 10 tight sandstone reservoirs in the X area as the research object,and obtained the geological characteristics of the reservoir by means of X-ray diffraction analysis,scanning electron microscopy,casting sheet and physical property analysis.Based on the physical properties,electrical properties,logging data and prefracturing data of the reservoir,the lower limit standard of each parameter of the volume fracturing geological “sweet spot” was determined: oil bearing grade is oil spot and above,core permeability is greater than or equal to 0.05×10-3μm~2,porosity is greater than or equal to7.3%,corresponding to acoustic time difference is greater than or equal to 212.06μs/m,the oil saturation is greater than or equal to 30%,and the resistivity is greater than or equal to 30?·m.In this paper,the rock triaxial stress experiment,the acoustic wave experiment and the tensile experiment were carried out to study the correlation of each parameter,to establish the dynamic and static parameter conversion relationship,to use the logging data to explain the rock mechanical parameters of the target layer of 18 experimental wells,and use this to calculate the brittleness index and fracture toughness index.The geostress test of acoustic emission Kaiser effect was carried out,and the geostress was interpreted using the geostress calculation model proposed by Professor Huang Rongzun to obtain the geostress stress parameters of the target layer of 18 experimental wells.Three kinds of fracturingability models were established by considering brittleness index,fracture toughness index and ground stress in turn.The optimum selection criteria of volume fracturing engineering "sweet spot" were determined synthetically: Class Ⅰ engineering "sweet spot" reservoir has the best fracturability(B is greater than 0.50,Frac is greater than 0.52,FI is greater than 0.31 m/MPa);Class Ⅱ engineering "sweet spot" reservoir has good fracturability(B between 0.45~0.50,Frac between 0.47~0.52,FI between 0.28~0.31 m/MPa);Class Ⅲ engineering "sweet spot" reservoir has poor fracturability(B less than 0.45,Frac less than 0.47,FI less than 0.28m/MPa).Finally,seven wells in the study area were verified and analyzed by using the established geological and engineering double "sweet spot" optimization standard,and the evaluation results matched well with the actual fracturing effect.It is verified that the establishment of volume fracturing geological and engineering double "sweet spot" optimization standards in this paper conforms to the actual situation on site and can be used to guide production development.