Geophysical research: article

Аnnotation: This paper presents a simplified mathematical model that can be used to describe the mechanical processes accompanying the drilling waste disposal by reinjecting it into rock formations. This technology helps to reduce environmental risks and increase the economic efficiency of drilling wells at hydrocarbon deposits. Which is especially evident and vital in development of the offshore deposits. Within the framework of the proposed model, the reinjection of drilling waste into the formation is descrides as the initiation of a hydraulic fracture in the target layer, where a mixture that can be represented by a nonlinear Bingham fluid is subsequently injected at certain intervals. Considerable attention is paid to the preventing of a fracture breakthrough into the overlying and underlying layers – a situation that has significant environmental consequences and is unacceptable when implementing the specified technology. It is demonstrated that redistribution of pressures in the target layer caused by the injection of drilling waste leads to an increase in effective compressive stresses in the target layer and a decrease in the critical pressure corresponding to a fracture breakthrough into the sealing layer. This result allowed to formulate recommendations for changing the volumes of drilling waste reinjection into layers based on the monitoring of instantaneous and total fracture closure pressure – in this paper the closure pressure was analysed using G-function apparatus. The proposed mathematical model is based on the best practices of the Russian company Sakhalin Energy LLC and is verified on real data of drilling waste reinjection during the development of the offshore hydrocarbon deposit of the Sakhalin-2 project. The possibility of using the model to determine the recommended injection regimes and to adapt the actual regimes to prevent breakthroughs is demonstrated.