Defining the Fracturing of Carbonate Reservoirs After Multistage Hydraulic Fracturing

Hydraulic fracturing is fundamental to optimizing the development of carbonate reservoirs at fields on the western slope of the South Tatar arch in the Republic of Tatarstan. The importance of hydraulic fracturing is becoming increasingly decisive for the exploration of oil fields as the total scope of hydraulic fracturing is increasing and, consequently, the share of man-made fracturing is also increasing. The paper proposes a solution to the problem of obtaining reliable data on the nature of newly formed conducting structures and the seepage flows of formation fluids during the development of producing formations, faced by oil and gas field operators. The article also provides the analysis results of the properties of a man-made fracturing and their spatial propagation, triggered by multistage fracturing (MSHF) in horizontal well ends. The studies revealed that increased volume of proppant injection leads to an expansion of fracture's dimensions, the length being more and the height much less, while the intensity of microseismic emission is correlated with the proppant flow rate. In the process of hydraulic fracture formation, concurrent activation of the existing natural fractures occurs. Increasing the injection volume leads to greater spatial coverage of the reactivation area of existing fractures. Based on the concept of critically stressed state of the rock massif, the obtained network of natural fracturing has been schematized. The identified fractures can be grouped into fracture systems with conditional kinematics according to the Coulomb-Anderson model as reverse faults of northwest extension with the azimuth of 146.79° (326.79°), as normal faults based on azimuth of HF fractures, as strike-slip faults of northeast and west-northwest extension with azimuths of 24° (204°) and 95 (275°), respectively. The obtained results mostly confirm the common nature of the spatial variation, the causes of its occurrence, and progression of a field of fractures Besides, to increase the efficiency of well operation the technology of gas evacuation from annular space of the well and its partial utilization by means of KOGS compressor unit was applied at the wells under examination (3292 and 3294).