Calculation of specific surface area for tight rock characterization through high-pressure mercury intrusion

As one of the unconventional oil and gas resources, tight oil is of great development prospect all over the world. The characterization of tight reservoir has important guiding significance for overcoming the problems in exploration as well as improving the development effect. As one of the characteristics of reservoir cores, the specific surface area is very important for the characterization of tight reservoirs. In this study, based on mercury injection data of tight reservoir core from Changqing Oilfield, through the establishment of equal diameter pore model, the specific surface area of pores corresponding to different radii is calculated, respectively, and the overall specific surface area of the core is obtained. Through the comprehensive evaluation of the mercury injection data and the calculation results, it is found that the pores with the medium radius (0.009-0.178 mu m) have the greatest contribution to the pore volume, followed by the pores with smaller radius (0.004-0.007 mu m), and the pores with larger radius (0.268-53.835 mu m) have the least contribution to the pore volume. However, the pores with smaller radius (0.004-0.089 mu m) have the greatest contribution to the specific surface area, followed by the pore with larger radius (0.133-6.666 mu m), and the specific surface area of individual pores in the middle range (8.917 mu m) has the least contribution. Therefore, the adsorption loss of surfactant and so on must be considered in the process of tight oil development. In the development process, a series of main technologies such as fracturing, new water/gas injection, and horizontal well development should be explored. Through the overall design and scale implementation of reservoir scale, the investment cost of unit-producing reserves can be effectively reduced, and ultimately, the maximum benefit of tight oil development can be realized.