This paper presents the implementation of a novel approach for efficient well placement design based on the dynamic characteristic of the reservoir without the need to run flow simulation. The approach uses State-of-the-Art Technology called the Fast Marching Method (FMM) coupled with Geometric Pressure Approximation to define a Dynamic Reservoir Quality Map. This map is also referred to as the Depletion Capacity (DC) Map. It provides the mapping of future potential locations to further deplete the reservoir.
The DC Map is generated by calculating 4 important factors, namely Pore Volume, Mobility of the Hydrocarbon, Reservoir Energy, and the Undrained Volume of the reservoir. The major breakthrough in using this technology is the ability to estimate the pressure distribution (i.e., reservoir energy) and drainage volume (i.e., to estimate the undrained volume) efficiently. These are the 2 factors that are difficult to obtain without conducting traditional flow simulation. The two aforementioned factors were obtained by calculating the FMM diffusive time of flight which can be related to the pressure drop by the Geometric Pressure Approximation theory. Thus, in effect, this calculation represents a pseudo-simulation, which is orders of magnitude faster than conventional simulation. The technique is applicable for both fine scale and coarse scale models with large number of realizations representing geological uncertainties. This approach works well in capturing the primary depletion phenomenon.
In this paper, we demonstrate the evaluation of existing well placement of an actual developed field, with 16 wells, located in Tarim Basin, West China, by comparing it to a new design. Additionally, the method is also used to propose future locations for infill drilling. The study is motivated by the big challenges faced when drilling a well at a depth between 6800 m–8000 m. Optimum well placement has the potential to drill optimum number of wells to produce the same reserves.
The new design was created with a scenario where 5 exploration wells that been put into production for a couple of years to represent the early depleted condition. The results show the optimum design can be achieved with only 12 wells. A saving of 4 wells compared to the existing well pattern. This is a significant saving considering the drilling challenges.
For the infill drilling, the study shows that for this reservoir, adding more wells may not be beneficial from the ultimate recovery point of view but production can be accelerated by drilling up to 2 more wells at the best potential locations as suggested by the DC Map. Best of all, the proposed method optimizes the locations very quickly.