Publications

In many cases, post-fracture production performance is significantly lower than the predicted production at the design stage and even from the post-fracture geometry and production simulations from the widely known pressure-matching technique. The geomechanics used in these simulations are often oversimplified with many assumptions, though accuracy is claimed on the basis that the stress profile is calibrated with the closure pressure interpreted from mini-fracture tests. The significance of comprehensive geomechanics for fracture growth modelling and production performance prediction is often underestimated. Consequently, the underperformance of fracture treatments is attributed either to formation damage, proppant crushing, or embedment, or to poor reservoir quality - despite a reasonably good reservoir property indicator from all sources including mini-fracture pressure decline. The main objective of this paper is to demonstrate how some of these simplified stress calibration techniques can produce significantly different stress contrast profiles compared to a profile that can be created based on the complete physics of geomechanics. Although all these profiles are calibrated with the same closure pressure from a mini-fracture test, the stress contrast between sand and shale becomes significantly different. Primarily, the use of an incorrect stress contrast profile from inaccurate or oversimplified calibration in prefracture designs and post-fracture pressure-matching simulations predicts unrealistically productive fractures that never produce consistently with the over-prediction. This paper references fracture treatments in a field in the Sumatra basin to highlight a number of inaccurate or oversimplified practices that prevail in the industry. In addition, the paper presents a more accurate approach to understand the post-fracture production performance by using a comprehensive and valid geomechanical model that leads to treatment optimization for future operations in the field.