Characterization of Hydraulic-Fracture Geometry in Shale-Gas Reservoirs
Authors: Carpenter Chris 
Published: February 2015

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 16896, ’Characterization of Hydraulic-Fracture Geometry in Shale-Gas Reservoirs by Use of Early Production Data,’ by Chunlou Li, Randy LaFollette, Andy Sookprasong, and Sharon Wang, Baker Hughes, prepared for the 2013 International Petroleum Technology Conference, Beijing, 26-28 March. The paper has not been peer reviewed.

Drilling long horizontal wellbores and completing wells with multistage fracturing are common practices in shaleplay development. One of the keys to enhancing production of these ultratight reservoirs is the creation of a complex_fracture system with very high surface area. Results of the current study show that post-treatment production data exhibit distinct features associated with various fracture systems and should be able to aid in describing the complex fracture system. The primary objective of this work was to find correlations between early-time production signatures and the fracture network.

Introduction

Hydraulic fracturing has long been an effective technique for stimulating low-permeability reservoirs. To simplify fracture modeling, biwing single-plane fracture geometry was often assumed from prefracture design through post-fracturing evaluation. However, fractures in the real world have been documented to be much more complex. Especially for economic shale plays, hydraulic-fracture interaction with natural fractures may result in complex fracture-network development. The biwing-fracture parameters—length, height, width, and conductivity—are not sufficiently detailed to describe complex fractures. Instead, another set of parameters—fracture density, unpropped- and propped-fracture conductivity, and stimulated-reservoir volume (SRV)—may be more-appropriate parameters to consider in both fracture design and production modeling.

After fracturing treatments, characterization of created fracture profiles helps engineers to understand the reservoir better and thereby to optimize subsequent well completions. Various fracture-diagnostic technologies were developed to describe the fracture parameters involved: orientation, length, height, width, and conductivity. These fracture-diagnostic techniques have been applied mainly to estimate biwing-fracture geometry. When applied to shale-gas wells, some of them fail to provide helpful information because of the complexity of the created fracture network.

Microseismic mapping is a technique that is widely accepted to characterize complex fracture networks. However, it is difficult to estimate the effectiveness of stimulation treatments directly from microseismic mapping because the location of proppant and the distribution of conductivity in the fracture network cannot be determined from microseismic data.

Direct fracture-diagnostic methods and production-analysis techniques are beyond the scope of this work. But, informed by the ideas underlying those techniques, this paper attempts to identify possible correlations between early-time production signatures and complex-fracture-system parameters.