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Computational Model Predicts Breakdown Pressures in Unconventional Plays

Unconventional shale reservoirs are characterized by extreme low permeability and high in-situ stress. Multistage hydraulic fracturing plays a key role in developing such reservoirs. However, depending on the in-situ stress magnitude or regime, breakdown pressures can be too extreme to achieve, given available surface horsepower and downhole completion capabilities. This paper presents a newly developed model to predict the breakdown pressures in cased and perforated wells.

Introduction

In unconventional shale reservoirs, multi­stage hydraulic fracturing often is applied to stimulate a number of clusters across the target zone. Once the clusters are perforated and hydraulic fracturing is applied, these clusters initiate transverse fractures, creating a fracture network that is required for reservoir depletion. At each cluster, the pressure delivered from the surface pumping units is exerted on the rock until the breakdown pressure is achieved. If the breakdown pressure is not achieved at a given cluster, there will be no induced fractures and, consequently, no production.

The main objective of the author’s study is to investigate the physics behind fracture initiation of cased and perforated wells in extremely tight reservoirs. This involves building a computational model to calculate the breakdown pressure for an inclined well at given azimuth and inclination angles. The developed model considers the in-situ stress magnitudes and faulting stress regimes to analyze local stresses around the perforations to predict the fracture-initiation pressure and orientation. Fracture propagation is outside of the scope of study.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 194038 STU, “A New Computational Model To Predict Breakdown Pressures in Cased and Perforated Wells in Unconventional Reservoirs,” by Mohammed Kurdi, University of New South Wales, prepared for the 2018 SPE Annual Technical Conference and Exhibition, Dallas, 24–26 September. The paper has not been peer reviewed.
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Computational Model Predicts Breakdown Pressures in Unconventional Plays

01 June 2019

Volume: 71 | Issue: 6

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