THE RECOGNITION AND ALLEVIATION OF COMPLEXITY WITH HYDRAULIC FRACTURING ONSHORE AUSTRALIA

Abstract

Increasingly demanding contractual obligations and more cost-effective technology has led to the widespread use of hydraulic fracture treatments of wells onshore Australia. Whilst historically confined to low permeability, marginal fields, the majority of natural gas wells in some areas of onshore Australia are now routinely hydraulically fractured. However, a number of wells in localised regions have displayed treatment difficulties. Such wells consistently display common symptoms, such as the inability to inject proppant at required concentrations without exceeding surface injection pressure limitations. Fracture treatments on these wells are often prematurely terminated (or 'screen-out'), mainly because of near-wellbore fracture complexity. Such wells invariably display poor post-stimulation productivity.

This paper describes the evaluation of reservoirs on the basis of in-situ stress and their propensity for fracture complexity. Simple, recognisable treatment pressure signatures, which indicate the presence of near-wellbore tortuosity, are presented. A conventional single, planar fracture simulation model confirms the presence of fracture tortuosity. Proppant-free shear dilation, herein referred to as a 'water-frac', has been analysed as an alternative fracture treatment in which natural fractures are inflated to interconnect with each other, forming a conduit for hydrocarbon flow. This alleviates near- wellbore fracture complexity and may avoid the expenditure of hundreds of thousands of dollars on sub- optimal fracture treatments or remedial work.