This paper is a continuation of the paper 1 (SPE-171882-MS, ADIPEC 2014) and addresses the second aspect of the study: "forward fracture modelling". The paper demonstrates the integration between the Pressure Transient Analysis (PTA) of the field data discussed in paper 1 and the fracture simulation to validate the forward fracture modelling results.
Fracture modelling work performed pre-dominantly in two Shell in-house fracture simulators – standalone pseudo-three-dimensional fracture simulator and coupled reservoir-fracture simulator (also referred as dynamic fracture simulator in this paper), for a horizontal water injector in an offshore field in South-East Asia will be presented. A methodology will be discussed for setting-up a relatively simple fracture model in the standalone simulator as well as a sophisticated 3D model in the dynamic fracture simulator. Fracture prediction runs from the two simulators will be discussed with an emphasis on the consistency of results between them. Further, uncertainties in fracture growth have been characterized in this study with an extensive list of parameters pertaining to three major domains – reservoir properties, geomechanical properties and operating conditions. We will discuss these uncertainty/design parameters and their impact on the fracture growth using the two simulators. We will also illustrate the approach of "Design of Experiments" for fracture growth sensitivity analysis with the help of the dynamic fracture simulator coupled with an in-house stochastic uncertainty management tool. Finally, probability distribution function for the fracture dimensions will be shown as an outcome of the sensitivity analysis.
The paper will conclude with the significance of forward fracture modelling, its validation with the PTA, and the contributions it can make in understanding the waterflood performance in the field. The paper will demonstrate how the study can benefit an asset team in identifying the reasons behind pre-matured water breakthrough in producers, understanding the impact of operating variables on fracture growth and hence, sweep, redesigning water injection operating envelopes, and addressing the field issues which altogether lead to the top quartile performance of the waterflood in the field.