Abstract

This paper describes how Reservoir to Surface Integrated Asset Models (IAM) were used to assess the production profile of a Coal Seam Gas (CSG) development. Specific attention is made to the modelling of the typical production phases of CSG systems such as the dewatering, gas production desorption initiation, switch from artificial lift production to natural flow and the decline of the field. Integrated Reservoir and Production Modelling is largely used within the Oil and Gas industry, ensuring that production predictions capture the required interactions from subsurface to surface. In this paper, the history matched numerical reservoir model is coupled to a well and network model to assess the long term production profiles while taking into account the operating logic of the CSG field. Specific modelling features are used in order to model the CSG PCP lifted wells producing the water phase through the tubing and the gas phase through the annulus into water and gas dedicated surface networks. While most of CSG production profiles are generated using specific harmonic decline techniques, the promoted methodology using IAM captures the behavior and the complex interactions between the surface and subsurface CSG models for the different outflow configurations. It enables to narrow the bottom hole pressure range for abandonment which is driving the final gas recovery of the field. Finally, an optimization logic workflow based on the outflow performance of the well was developed in order to determine the optimum date to switch from PCP lifted to natural flow and then back to PCP lifted at the end of the field life. This case study provides an example of the IAM model built for a Coal Bed Methane reservoir and offers valuable insights about how Integrated Asset Modeling enables a decrease of the investment risk associated with the development of such fields.

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