Abstract

Xanthan Gum has been used extensively as a viscosifier in the oil industry for different applications due to its unique rheological properties. An experimental study has been conducted to investigate the formation damage characteristics of Xanthan Gum based fluids and the results are presented in this paper.

A series of core flow experiments have been conducted to investigate the possible relationship among the Xanthan Gum concentration, fluid extensional viscosity, shear viscosity, filtration loss characteristics, pressure drop across the core samples and hence, any change in the original permeability of the porous media.

Results of extensional and shear viscosity measurements, API filtration loss tests, and formation damage tests conducted by using fluids of different xanthan gum concentrations are shown in this paper.

Introduction

The economic impact of poor productivity of openhole wells has pushed operators, service companies, and other research institutions towards spending significant research efforts in recent years to investigate drilling, completion and stimulation induced formation damage.1–13

Despite all the efforts, questions still remain regarding the formulation of optimum fluid composition to minimize productivity impairment due to formation damage.

The rate of fluid filtration into the reservoir rock (leak-off rate) is one of the most critical parameters that needs to be controlled carefully during drilling, completion and stimulation operations. A strict control of fluid filtration characteristics is required to limit borehole instability, excessive torque and drag, pressure differential sticking and formation damage. 14 The problem becomes even more critical when drilling/completing with water based fluids where the fluid remain in contact with the pay zone for a long period.

Fluid loss control in solids-free brines is generally achieved by; increasing the viscosity of the fluid5–16 and developing internal/external filter cake using lost control additives17. In a recent study, Svendsen et al. 18 has shown that extensional viscosity can be successfully used to establish an internal filter cake in association with a coiled tubing drilling fluid application. If the viscosifiers and fluid loss control additives are not selected properly, both mechanisms may lead to significant reduction of permeability.

Xanthan gum has been used extensively as a viscosifier in the oil industry for drilling, well completion, well stimulation and even for enhanced oil recovery applications due to its unique rheological properties. Formation damage characteristics of xanthan gum based fluids have been investigated and the results are presented in this paper.

Xanthan Gum

Xanthan gum, an exocellular heteropolysaccharide produced in fermentation by bacteria (Xanthomonas campestris), is a cream-colored powder that dissolves in water to produce solutions with high viscosity at low concentration. 19

Xanthan gum has relatively stable viscosity properties as a function of salt concentration, pH, temperature and shear degradation. 20

Xanthan gum's high viscosifying ability, coupled with excellent stability under high salinity, high temperature, and mechanical shear conditions makes the use of xanthan gum favorable for various drilling, drillin, completion, fracturing and even in enhanced oil recovery (EOR) operations in the oil field 19–22. In a recent study, however, Saasen and Loklingholm23 reported that poor whole cleaning is obtained if xanthan gum is used as a primary viscosifying additive in s

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