Single stage filter cake removal of barite weighted water based drilling fluid

Abstract

The removal of barite filter cake is a challenging problem because the conventional filter cake removal treatments that use hydrochloric acid (HCl) or chelating agents were ineffective in dissolving barite containing filter cakes. Barite, or barium sulfate, is insoluble in water and acids such as HCl, formic, citric, and acetic acids. Also barite has very low solubility in chelating agents such as Ethylene diamine tetra acetic acid (EDTA) and Diethylene triamine penta acetic acid (DTPA).The present study focuses on developing new formulation to remove the barite filter cake. The removal formulation consists of chelating agents such as Diethylene Triamine Penta acetic Acid (DTPA), converting agent or catalyst, and polymer breaker (Enzyme). Solubility tests of industrial barite and solids collected from de-sanders during well flow back were conducted to develop barite removing solvent. Actual barite drilling fluid samples were collected from the field during drilling a high pressure high temperature deep gas well. The performance of the designed formulation was examined to remove the filter cake formed by real drilling fluid samples collected during drilling operations using High Pressure High Temperature cell (HPHT).Based on the result of this work the filter cake removing formulation dissolved more than 90% of the filter cake formed by real barite drilling fluid in a single stage within 24h. The removal formulation consists of high pH potassium base DTPA of 20wt% concentration, enzyme as a polymer degrading agent, and one of the following converting/catalytic agents (potassium carbonate, potassium formate, or potassium chloride). The use of converting agents increased the barite solubility from 67–95%.