Acid-Sludge Characterization and Remediation Improve Well Productivity and Save Costs in the Permian Basin

Abstract

Many oil wells in the Permian Basin have reported sludging problems associated with acid stimulations. The acid sludge is similar among wells and was identified as a viscous emulsion stabilized by asphaltene-rich organic solids. The sludging tendency of the oil increased with the concentrations of asphaltenes and resins, base number of the oil, and ferric ion content in the acid. Only three out of nine commercial acid systems tested were effective in preventing acid sludge formation; they all utilize the same novel iron control technology, i.e., catalytic reduction of ferric ions. Several commercial and generic solvent systems were effective in dissolving acid sludge, induding mixtures of an aromatic solvent (e.g. xylene) with either isopropyl alcohol (2: 1 volume ratio) or EGMBE (2: 1 to 3: 1 volume ratios). Selection of acid formulations and solvent systems was based on cost effectiveness and operation safety. Field implementation proved successful. If the results of this study had been implemented earlier in the lives of some of the Permian Basin properties, the recovery of 574 BOPD of lost or deferred production from 99 wells could have been realized. This would have resulted in an estimated increased revenue of over $3 million in one year.

Improving Wellbore And Formation Cleaning Efficiencies With Environmental Solvents And Pickling Solutions

“…9,20,21,25 Another significant challenge in acid stimulation is the inducement of damaging asphaltic sludges by the incompatibility of spent acid and certain formation crudes, which can be exacerbated by the presence of ferric iron. 7,8,13,27,28 Both ferric and ferrous iron promote sludging,…”

Disaggregation and discretization methods for formation damage estimation in oil and gas fields: an overview

“…Once a model has been validated, it can be used to simulate with great precision the formation damage and the effectiveness of treatments for its inhibition and remediation. However, current techniques for reservoir characterization by historical comparison do not consider changes in the formation properties through the productive life of the reservoir Hence, models that can characterize the variations of these variables accurately through time using a history match are necessary to predict future performance [16][17][18] precisely. Thereby, the methodology for diagnosis, quantification, disaggregation, and characterization of formation damage processes allows the engineer to formulate an effective treatment that achieves to prevent, remove, and inhibit the damage mechanisms of greater relevance that are affecting the productivity [16].…”

“…consider the monetary factor in terms of the treatments implemented in oil fields in the past [17]. Nevertheless, remediation operations without a conscientious design could lead to additional formation damage mechanisms [18]. Hence, different authors have developed methodologies that allow determining and quantify the impact of each of the sources of damage, ensuring successful and cost-effective remediation and inhibition interventions.…”