Overcoming Hydraulic Fracturing Challenges in High Temperature and Tight Gas Reservoirs of Saudi Arabia with an Enhanced Fracturing Fluid System
Authors: Al-Driweesh S.  M. , Dashash Alaa A. , Malik Ataur R. , Leal Jairo , Soriano Eduardo , Lopez Alfredo 
Published: March 2015

Hydraulic fracturing has been an important aspect on the successful exploitation of gas sandstone formations in Saudi Arabia. During the past decade, conventional formations were stimulated successfully with traditional low to moderate temperature borate crosslinked based fracturing fluids. As the development of the existing fields continue into deeper formations and the exploration activities are inclined toward unconventional reservoirs, new challenges are experienced from lower permeabilities and higher temperatures. The conventional borate crosslinked gels are no longer the choice of fracturing fluids for extreme bottom-hole conditions.

To overcome these challenges, an improved, salt-compatible, low-polymer, organometallic crosslinked-gel (CMHPG) as fracturing fluid has been introduced for high-temperature (HT) wells. The novel HT fluid provides excellent proppant transport capabilities at temperatures ranging from 60 to 375 °F, while using fracture fluid requires less base polymer that results in less formation damage and higher retained conductivity of the propped fracture. This property is especially valuable in low-permeability reservoirs, where extended fracture lengths are typically required to maximize reservoir contact and enhance production. Additionally this fluid has been enhanced with a microemulsion surfactant to obtain a higher load recovery and also a novel clay stabilizer specially designed for tight gas and shale formations.

This paper addresses the successful application of this enhanced fracturing fluid in HT and tight gas wells of Saudi Arabia along with its post-treatment evaluation comparing dimensionless productivity index between fracture treatments with new and conventional fracturing fluids.

Introduction

Gas reservoirs have been exploited in Saudi Arabia for the past decade using hydraulic fracturing in vertical and horizontal wells where bottom-hole temperatures were mostly limited to 300 ???F. These reservoirs were stimulated successfully with traditional borate crosslinked fracturing fluids. In recent years, Saudi Arabia has launched projects to exploit and develop its deeper tight and shale resources; however the formations normally found are extremely complex in terms of heterogeneity, high reservoir pressure (up to 11,000 psi) high temperature (up to 350 F) and high stress (up to 1.1 psi/ft). Considering these complexities, conventional borate based crosslinked polymer guar gel as fracturing fluid is outside of the optimum envelope as far as required rheology is concerned and exhibits extreme sensitivity to mixed water, KCl quality and other fluid additives. Thus, conventional fluid formulation need to be revised from one well to the other through time consuming laboratory experiments and often required fluids characteristics are not achievable at bottom-hole (bh) conditions. To overcome these issues with conventional borate crosslinked gel, novel organometallic crosslinked fracturing fluids were introduced. The commercial production in these challenging reservoirs require stable fracturing fluids to place optimum fractures followed by quick unloading of fracturing fluids to maximize proppant pack conductivity. To meet these objectives, the surfactant and breaker package must be engineered optimally in novel organometallic crosslinked gel.