New Visco-Elastic Surfactant Formulations Extend Simultaneous Gravel-Packing and Cake-Cleanup Technique to Higher-Pressure and Higher-Temperature Horizontal Open-Hole Completions: Laboratory Development and a Field Case History From the North Sea.

Abstract

Filter-cake cleanup in open-hole gravel-pack completions has traditionally involved several stages: gravel-packing, pulling out of the hole with the work string, running in hole with production tubing, running in hole with coiled tubing, circulating the excess carrier fluid from inside the base pipe and spotting a breaker solution. Furthermore, in cases where removal of both the polymeric components and the CaCO3 bridging agents is necessary, an enzyme or an oxidizer soak has typically been followed by an acid treatment. This process is time consuming and costly, in addition to being non-optimal in terms of uniform cake-cleanup in long open-hole completions, due to rapid reaction between acid and CaCO3 particles. Recently proposed simultaneous gravel-packing and cake-cleanup method incorporating breakers into the gravelpack carrier fluid have been demonstrated to be an efficient technique through more than a dozen field applications, as evidenced by higher productivity compared to offset wells completed with conventional techniques. Because of the inherent risk in simultaneous gravel-packing and cake-cleanup with water-packing technique, carrier fluids containing breakers for filtercake removal have been used in conjunction with shunt-packing, which has been demonstrated through both field applications and large-scale yard testing not to rely on either the filter-cake or the formation properties. However, because shunt technique relies on viscosity for gravel placement, application of the simultaneous gravel-packing and cake-cleanup technique with polymer-free visco-elasticsurfactant (VES) carrier fluids has been limited to wells requiring a density of about 9.8 ppg (for circulating packs) and a bottom hole circulating temperature less than 200°F. In this paper, we present new surfactant formulations, which have unique chemistry that allows them to form visco-elastic surfactant solutions in high-density brines and remain stable at elevated temperatures. Densities up to 13.8 ppg with a rheological profile suitable for shunt-packing at bottom hole circulating temperatures exceeding 250°F are achievable with this new surfactant, covering a large majority of the gravelpack applications. It is further demonstrated that this new surfactant system does not only allow the use of certain chemicals that can be used for CaCO3 dissolution in conjunction with a gravel-pack process, but also requires these chemicals as co-surfactants in order to develop a visco-elastic structure. In addition to discussion of the unique chemistry of this VES formulation, data pertaining to proposed gravel-pack applications are presented. These include rheology, gravel suspension properties, filtercake dissolution characteristics, and retained permeabilities. A field case history utilizing the new VES fluid incorporating filter-cake cleanup chemicals is also detailed.

Recent Advances in Viscoelastic Surfactants for Improved Production From Hydrocarbon Reservoirs

“…Other uses for VESbased fluids such as filter-cake cleanup after gravel packing are also noted (Daniel et al 2002;Godwin et al 2002). Substantial recent developments in the areas of hydraulic fracturing and matrix acidizing have been seen over the last decade and will be discussed in greater detail.…”

“…Hydraulic-fracturing VES-based fluids that are composed of anionic surfactants such as alkyl sarcosinates have been reported and can also be applied to gravel packing, frac packing, and water-control issues (Di Lullo Arias et al 2002). The fracturing fluid includes a combination of a water-soluble salt such as potassium or sodium chloride, 0.5-6 wt% alkyl sarcosinate surfactant, a buffer for adjusting the pH to 6.5-10, and either 0.1-2 wt% carboxylic acid salt as an additional source of ions or, alternatively, 3-6 wt% chloride or fluoride salts.…”

Friction Pressure Performance of Commonly Used Viscous Gravel-Packing Fluids

“…Commonly used fluids are VESs as discussed in Daniel et al (2002), Campbell et al (2002), and Whaley et al (2007); polymer-based fluids such as xanthan discussed in Nguyen and LaFontaine (1990) and Underdown et al (1989); and HEC discussed in Underdown et al (1989) and Cole and Ali (1994). These fluids are non-Newtonian, exhibiting shear-thinning behavior.…”

Application of a New Class of Surfactants in Stimulation Treatments

“…Application of a New Class of Surfactants in Stimulation Treatments Hisham A. Nasr-El-Din, SPE, Saudi Aramco; Elsamma Samuel and Mathew Samuel, SPE, Schlumberger years of successful use of VES systems in hydraulic fracturing, its use is now extended to many applications including diversion, [13][14][15] matrix stimulation, [16][17][18] sand control, 20 acid fracturing, 21,22 fluid-loss control 23 and CT cleanout. 24 The objectives of this paper are to review the performance of VES in various applications and discuss their performance based on field data.…”