Acid Fracturing HT/HP Gas Wells Using a Novel Surfactant Based Fluid System (2003)

Acid Fracturing HT/HP Gas Wells Using a Novel Surfactant Based Fluid System Hisham A. Nasr-El-Din; Hisham A. Nasr-El-Din Saudi Aramco Search for other works by this author on: This Site Google Scholar Saad Al-Driweesh; Saad Al-Driweesh Saudi Aramco Search for other works by this author on: This Site Google Scholar Ghaithan A. Al-Muntasheri; Ghaithan A. Al-Muntasheri Saudi Aramco Search for other works by this author on: This Site Google Scholar Richard Marcinew; Richard Marcinew Schlumberger Search for other works by this author on: This Site Google Scholar John Daniels; John Daniels Schlumberger Search for other works by this author on: This Site Google Scholar Mathew Samuel Mathew Samuel Schlumberger Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Annual Technical Conference and Exhibition, Denver, Colorado, October 2003. Paper Number: SPE-84516-MS https://doi.org/10.2118/84516-MS Published: October 05 2003 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Nasr-El-Din, Hisham A., Al-Driweesh, Saad, Al-Muntasheri, Ghaithan A., Marcinew, Richard, Daniels, John, and Mathew Samuel. "Acid Fracturing HT/HP Gas Wells Using a Novel Surfactant Based Fluid System." Paper presented at the SPE Annual Technical Conference and Exhibition, Denver, Colorado, October 2003. doi: https://doi.org/10.2118/84516-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 Annual Technical Conference and Exhibition Search Advanced Search AbstractDuring acid fracturing of carbonate reservoirs, the acid dissolves the rock, creating wormholes which increase fluid loss. Excessive fluid loss lowers the net pressure in the fracture limiting fracture extension, and adversely affects the conductivity of the fracture. To overcome this problem, multiple stages of polymer pads are usually pumped in acid fracturing treatments to reduce leak-off. In addition, synthetic polymers are commonly added to the acid to produce gelled or in-situ gelled acids. The objective of adding these polymers is to reduce leak-off, by increasing the viscosity of the acid. This in turn reduces the rate of mass transfer of the acid to the rock surface. However, several studies have shown that these polymers can cause formation damage. Moreover, the crosslinker can precipitate in the formation causing further damage. Efficient mixing of synthetic polymers in the field is also a concern, especially when the polymers are present in a solid form.To overcome problems associated with polymeric fluids, polymer-free fluids were used for the first time to acid fracture several vertical wells in a deep gas reservoir in Saudi Arabia. The acid fracture treatments consisted of several stages including: viscous pads, emulsified acid, in-situ acid and an inhibited acid. A visco-elastic surfactant system replaced the polymers used in the pad and the leak-off control acid (28 wt% HCl). Calcium chloride produced from acid reactions with the carbonate rock viscosifies the acid in-situ, reducing leak-off volume.ResultsThe pressure response to acid fracture treatments clearly indicates that the surfactant-based system is very effective in controlling acid leak-off during the treatment in wells with a bottom hole temperature of nearly 260°F. Good leak-off control did help in maintaining a constant pumping rate throughout the treatment. Significant increases in both gas production and flowing wellhead pressures were achieved utilizing this new system. In addition, pumping operations were simplified by continuous mixing of the fluids. The nondamaging nature of the system enhanced production rates above expectations.IntroductionSaudi Aramco has embarked on an aggressive program to develop its gas fields. The unassociated gas is being produced from two main reservoirs: J (sandstone) and K (carbonate). Hydraulic fracturing is used to enhance gas production from the sandstone reservoir, while acid fracturing is used to increase gas production from the carbonate reservoir.1,2 The present paper will focus on acid fracturing of the carbonate reservoir.The K-formation, which lies between 11,000 and 12,000 ft, is of late Permian age and is divided into four intervals. The two main producing zones are the K-B and K-C, which produce both gas and condensate. These heterogeneous zones are mainly composed of dolomite with streaks of calcite and anhydrite. This type of composition makes them highly soluble carbonates and excellent candidates for acidizing treatments. However, the BHST in this reservoir varies between 250 and 280°F, which presents a challenge in any acid treatment design. High bottom hole temperatures increase the rate of mass transfer of the acid, which causes the acid to spend quickly in the formation. Another problem is the corrosive nature of the acid at higher temperatures, which requires higher inhibitor loadings. Inhibitor aids will also be needed if the bottom hole temperatures exceed 200–220°F.The K-reservoir is also classified as a moderately permeable to tight gas reservoir, which has a porosity ranging from 1 to 25 vol% in the higher porosity sections. These types of porosities, coupled with the natural fractures present in the zone, result in undesirably high leak-off rates. An acid fracturing treatment can increase the permeability of these fractures several thousand-fold, making leak-off control an even greater challenge. Keywords: drilling fluid selection and formulation, acid, calcium, permeability, hydraulic fracturing, drilling fluid property, dolomite, drilling fluid chemistry, flowback time, exhibition Subjects: Drilling Fluids and Materials, Hydraulic Fracturing, Drilling fluid selection and formulation (chemistry, properties) This content is only available via PDF. 2003. Society of Petroleum Engineers You can access this article if you purchase or spend a download.