Delayed-Release Acid System for Cleanup of Al Khalij Horizontal Openhole Drains

Abstract

Delayed-Release Acid System for Cleanup of Al Khalij Horizontal Openhole Drains Pierre Leschi; Pierre Leschi Total S.A. Search for other works by this author on: This Site Google Scholar Gilles Demarthon; Gilles Demarthon Total E&P Qatar Search for other works by this author on: This Site Google Scholar Eric Davidson; Eric Davidson Halliburton Energy Services Group Search for other works by this author on: This Site Google Scholar Duncan Clinch Duncan Clinch Halliburton Search for other works by this author on: This Site Google Scholar Paper presented at the SPE International Symposium and Exhibition on Formation Damage Control, Lafayette, Louisiana, USA, February 2006. Paper Number: SPE-98164-MS https://doi.org/10.2118/98164-MS Published: February 15 2006 Connected Content Related to: Delayed-Release Acid System for Cleanup of Al Khalij Horizontal Openhole Completions Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Leschi, Pierre, Demarthon, Gilles, Davidson, Eric, and Duncan Clinch. "Delayed-Release Acid System for Cleanup of Al Khalij Horizontal Openhole Drains." Paper presented at the SPE International Symposium and Exhibition on Formation Damage Control, Lafayette, Louisiana, USA, February 2006. doi: https://doi.org/10.2118/98164-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE International Conference and Exhibition on Formation Damage Control Search Advanced Search AbstractIt is well known that the use of hydrochloric acid to clean up and restore permeability of open holes drilled in limestone formations is a questionable procedure. It is necessary to remove, not only the filter cake at the well bore face but, more importantly, the low permeability crushed zone created during the drilling operation. To achieve uniform treatment of the entire openhole section with hydrochloric acid is difficult: the rapid reaction of the acid in downhole conditions often creates a localized loss zone, through which most of the treating fluid is lost so that treatment of the entire section is inefficient.Traditional completion practice on Al Khalij field (Qatar) involved cemented casing, perforations and subsequent stimulation of the limestone with retarded emulsified hydrochloric acid and ball sealers. This paper describes a new and different approach, which involves leaving drains in openhole condition and using a slow acting stimulation treatment for damage removal and stimulation. The stimulation treatment comprises a starch enzyme to degrade the most troublesome polymer and an organic compound that reacts with the carrier brine to release organic acid in situ over a period of several hours. The breaker fluid is introduced to the openhole section in a neutral pH condition, thus enabling it to be distributed over the entire interval of interest. Enough acid is generated over the subsequent 12 hours to remove the filter cake and clean up the crushed zone.This system has recently been used on several occasions on this field, with openhole drain length ranging from 530 to 1890 m (1,740 to 6,200 ft) and treatment volumes ranging from 20 to 115 m3 (125 to 725 bbl). Losses from these wells occurred after the predicted elapsed time. Details are provided of how the jobs were carried out and the results achieved.IntroductionThe Al Khalij offshore oilfield is in the northern part of the Qatar sector of the Arabian Gulf.The oil bearing Mishrif reservoir is a stratigraphic trap in the upper Cenomanian limestone. Laid down with several repeating phases of deposition and erosion, the reservoir typically consists of sequences (20 to 30 ft), each alternating between poor permeability matrix intervals and highly productive diagenetically weathered layers (drain layers)[1]. Permeability estimated from test data ranges between 100 mD to a few Darcy in drain layers but, in contrast, matrix permeability is 1 - 50 mD.The oil bearing strata are shallow at about 1200 m TVD. Total thickness of the Mishrif formation can be as much as 150 m (∼500 ft). The formation is normally pressured and bottomhole temperature is low at about 53°C.During the initial development stage of this field, it was considered that vertical or slightly deviated wells, activated by means of ESP (Electrical Submersible Pump), would be appropriate as it appeared that the natural high permeability drains could be expected to provide good productivity[2]. However, a change in plan was brought about when the drain permeability was found to be very irregular. Good permeability was found to occur in random zones of around 200 - 500 m and this prompted the decision to develop the field using horizontal wells[2], the intention being to drill very long horizontal sections to intersect the productive zones. Keywords: lateral, drilling operation, concentration, half life, acid, stimulation, filtercake, formic acid, Upstream Oil & Gas, Directional Drilling Subjects: Drilling Operations, Directional drilling This content is only available via PDF. 2006. Society of Petroleum Engineers You can access this article if you purchase or spend a download.