One of the plans for the production of Turkey’s largest oil reserve, Bati Raman (1.85 billion barrels), is to use Mining-Assisted Heavy Oil Production (MAHOP). In this method, twin declines are excavated from the surface to the reservoir and a series of excavations (galleries) continue along the bottom of the reservoir. Fan-shaped steam injection and production holes are drilled in the reservoir from the crown of the galleries to use conventional Steam-Assisted Gravity Drainage (SAGD). The Bati Raman reservoir is situated at an average depth of 1450 m, producing 12° API heavy oil from a 60m thick calcareous reservoir rock. This research aims to numerically investigate the stability of excavations together with the initiation, formation and propagation of fracture networks between the fan-shaped boreholes and around typical twin excavations using FLAC3D. It is shown that the stability of twin excavations and pillars between them can be guaranteed with suitable support types. In addition, this innovative approach in heavy oil production in hard rock media successfully showed that the fracture networks created by MAHOP could be used effectively for oil recovery of reservoir rocks using SAGD.
The increase in oil demand and the decrease in natural resources encourage engineers to try out innovative solutions for oil production. One solution is resorting to more efficient methods at more challenging conditions instead of conventional techniques. Heavy oil production at great depths by conventional methods requires such a solution. Crude oil with API gravity of 12° is classified as heavy oil that is heavier than water and sinks in it and requires heavy oil recovery techniques to be adopted to be produced. Numerous conventional heavy oil recovery methods are in use, such as drilling vertical wells, pumping and creating a high-pressure difference on oil. However, recovery rates of conventional methods are highly inefficient; for this reason, different technologies are adopted to develop efficient solutions such as thermal and cold methods by targeting two factors; gravity and the viscosity of heavy oil. These unconventional methods include Vapour Extraction (VAPEX) method, CO2, water and diluent steam injection techniques which is creating a vapour chamber in the reservoir by injecting vaporised solvents, Steam-Assisted Gravity Drainage (SAGD) method that is making the oil more mobile by injecting hot steam from one of the two parallel wells and collecting less viscous oil from the other. In general, steam usage in heavy oil production gives the most encouraging recovery rates, even if these methods have their unique challenges [1]. Another way for heavy oil production is Mining Assisted Heavy Oil Production (MAHOP). In this method, tunnels or shafts are used to reach the reservoir, and a series of excavations continue along the bottom of the reservoir. Fan-shaped steam injection and production holes are drilled in the reservoir from the galleries’ crown to use steam-assisted gravity drainage [2]. Steam injection is done from the bottom of the reservoir. The area that will be water-wetted is more controlled in creating a more accessible injection domain by considering the exposed reservoir surface and fractured rock mass induced by the excavations.