Abstract

The objective of the study is to develop an integrated multi-disciplinary workflow to screen wells for suitable candidates and to evaluate the feasibility of selected wells for refracturing using advanced geomechanical modeling.

A four-step workflow to select and evaluate wells for refracturing was developed. First, hundreds of wells were screened based on age, spacing, and production performances, mainly IP90 and IP30 to IP360 ratio. Second, the selected wells from the first step were furthered narrowed down by analyzing their original completion and stimulation. Wells that were under-stimulated compared to historical average stimulation metrics, i.e. fewer stages/clusters and larger spacing, lower proppant loading, and less fluid volume pumped, were chosen as the final candidates for geomechanical modeling. Third, the wells were modeled with in-house advanced geomechanical fracture simulation and then depleted to obtain current stresses state. Finally, the technical feasibility of refracturing the wells was assessed.

The workflow for best candidate selection has been improved considering volume of proppant placed, stress orientation, number of clusters / stages, reservoir quality, and production history.

Due to the low horizontal stress contrast (1[MMPA]), fine scale stress determination was required. A 3D initial stress model was available from a previous study. From this stress state geomechanical hydraulic fracture mapping was performed. This geomechanical modeling utilizes Zero Thickness Element (ZTE) technology and the fractures only open if achieving the energy criteria. The stimulated volume and stress changes due to hydraulic fracturing were modeled with high resolution unstructured grids. Fracture driven interaction such as stress shadowing, cluster interference and fractures interconnection were observed. Production history was modeled with equivalent volume to determine the stress changes from the most accurate fracture geometry.

The novelty is the systematic workflow integrating completion, production and geomechanics for selecting and evaluating the most suitable wells for refracturing, either stimulating new reservoir or reconnecting previous fractures. The advanced geomechanical techniques used to model the stresses at very fine scale and with unstructured grids are also state of the art.

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