Factors Affecting the Performance of Enzyme Breakers for Removal of Xanthan-Based Filter Cakes

Abstract

The use of enzymes as an external breaker for removal of xanthan based filter cakes has exhibited cost savings and effective clean up in several open-hole horizontal Gulf Coast wells. Enzymes are specialized proteins produced by cells of living organisms. They act as catalysts to promote specific reactions. Polymer-specific enzymes hydrolyze xanthan resulting in non-damaging fragments. As a catalyst, the structure of an enzyme is unchanged by the reaction it promotes; therefore, the enzyme has the ability to initiate another reaction. The reactivity of the enzyme is essentially infinite with the exception of damage to the enzyme by chemical, thermal, or mechanical means, i.e. denatured. Xanthan-specific enzymes degrade or cleave either the a - 1,2 or ß - 1,4 glycosidic linkages of the substituent and the ß - 1,4 linkages of the backbone. Recent laboratory investigations revealed several factors, which can control the effectiveness of an enzyme. These factors include xanthan quality, iron, base brine and hydrocarbons. These factors can function as barriers and prevent the enzyme from cleaving specific linkages of the xanthan structure. This study presents guidelines for formulating an enzyme compatible xanthan based drill-in fluid for open-hole horizontal completions. These guidelines were recently applied to two recent open-hole horizontal completions in the Gulf of Mexico that yielded optimum results. Introduction Drill-in fluids are typically comprised of starch, xanthan, and sized calcium carbonate or salt in a base brine. Although, drill-in fluids are inherently less damaging than the conventional drilling muds, relatively impermeable filter cakes are still deposited on the borehole walls. Partial removal of drill-in fluid filter cakes can significantly impede flow at the wellbore wall. This can result in significant reduction of the well productivity or injectivity. To realize the full potential of open-hole horizontal completions, formation damage from residual filter-cake must be eliminated. A common approach to minimizing such damage is the application of acids or strong oxidative breaker systems to dissolve filter cake solids and biopolymers. Field experience has demonstrated that an acid/oxidative breaker performs reasonably well in short to medium radius open-hole intervals. However, an acid/oxidative breaker appears to be less effective in extended reach open-hole intervals. The problem may be related to contact time of the highly reactive solution with the drill-in fluid damage creating "wormholes".

Developing novel bio-nano catalyst well clean up fluid to remove formation damage induced by polymeric water-based drilling fluids

“…Without using any acid, biological treatment and oxidizers demonstrated filter cake removal in a clean formation in stand-alone pre-packed screen, slotted-liner completion in the North Sea (Price-Smith et al, 1998). Non-specific enzymes randomly hydrolyze the polymers, producing insoluble crosslink chains and causing permeability damage (Luyster et al, 2000).…”

Wykorzystanie enzymów do udrażniania strefy przyodwiertowej po dowiercaniu

“…Proces hydrolizy celulozy składa się z następujących etapów: adsorpcji celulazy na powierzchni celulozy, degradacji celulozy do cukrów prostych oraz desorpcji celulazy z powierzchni materiału poddawanego hydrolizie; • mannanazy -rozkładające polimery zbudowane z mannozy, np. guar -niszczą każde wiązanie α-1,2-albo β-1,4glikozydowe z podstawnikiem oraz wiązanie β-1,4 ze szkieletem biopolimeru [6,7]. Enzymy te nie usuwają blokatora (np.…”

“…W literaturze zagranicznej dotyczącej stymulacji można znaleźć przykłady eksperymentów i praktycznych zastosowań ostatniej z wymienionych metod [1,6,8]. Zazwyczaj polegały one na równoczesnym zastosowaniu w odwiercie różnych enzymów w kombinacji z kwasami [3].…”

Research on New Materials to Improve the Bonding Strength and Relieve Contamination of the Cement Slurry with Oil Based Muds

“…Oxidizers as well as strong acids are considered as non-specific reactive types. They can also react with many different materials including treating lines, downhole tubulars, formation components and hydrocarbons [12,13]. So these materials can`t be supported in removal of filter-cake.…”