Field Application of Emulsified Acid-Based System to Stimulate Deep, Sour Gas Reservoirs in Saudi Arabia

Nasr-El-Din, H.A.; Solares, J.R.; Al-Mutairi, S.H.; Mahoney, M.D.

doi:10.2523/71693-ms

Cited by 48 publications

(19 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hence the selection of the right and well tested emulsifying agent is vital. 5,6,7 Acid covered with a film of diesel exhibit a much lower reaction rate and hence the solution becomes retarded. Laboratory testing on carbonate cores proved that the retardation factor can increase up to 13 times that of normal HCl acid for a given concentration.…”

Section: Fluid and Additives Selectionmentioning

confidence: 99%

Combining Selective Stimulation With Tailored Perforating Improves Injection Profile in a Carbonate Reservoir: A Case Study

Al-Gub¹,

Horikoshi²,

Ichikawa³

et al. 2010

Proceedings of North Africa Technical Conference and Exhibition

View full text Add to dashboard Cite

In a multi-layer heterogeneous carbonate reservoir in which production and injection is being carried out, one of the biggest challenges faced is to produce/inject evenly from/to the different layers. At elevated temperatures this heterogeneity limits the success of conventional stimulation techniques. A novel acid diversion technique involving selective stimulation and tailored perforation design techniques was applied in an offshore UAE well to improve injectivity in a multi-layered heterogeneous carbonate reservoir.The well in question was re-completed from a dual string water injector well to a single string gas injector re-perforated in four different sub-zones. Well test and production logging data were used to estimate permeability and flow profile before the workover. These data were then used to run NODAL analysis, stimulation simulation, and perforation simulation models. The final workover proposal called for:• Perforation over the same interval as was previously perforated using different gun and charge sizes to establish controlled injection based on the different zones permeability. • Optimized coiled tubing (CT) selective stimulation using high strength retarded acid pumped in stages with a self diverting acid.The well injection performance was dramatically improved as evidenced by the gross injection value and the injection profile obtained in a post treatment production logging run.This paper details the planning, execution and final evaluation of this job which is unique in that the same interval was tested twice, before and after workover, after being completed using different perforating and stimulation techniques. BackgroundCarbonate reservoirs tend to be complex and often exhibit large variations in permeability over different sections of the same producing zone 1 . These variations in the permeability profile create challenges when planning to inject acid (commonly done in carbonates), produce hydrocarbons, or inject water or gas. It is often the high permeability zones that will dominate while the lower permeability zones will miss the treatment or not be produced.

show abstract

Section: Fluid and Additives Selectionmentioning

confidence: 99%

Combining Selective Stimulation With Tailored Perforating Improves Injection Profile in a Carbonate Reservoir: A Case Study

Al-Gub¹,

Horikoshi²,

Ichikawa³

et al. 2010

Proceedings of North Africa Technical Conference and Exhibition

View full text Add to dashboard Cite

show abstract

“…The fluid's access to the rock face will be reduced through decreasing the rate of acid leak-off and acid mobility (Peters et al 1989). There are several options to lower the acid spending rate, such as the use of emulsified acids (Dill 1961;Knox and Lasater 1964;Crenshaw and Flippen 1968;Nasr-El-Din et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Acid Treatments in High Temperature Dolomitic Carbonate Reservoirs Using Emulsified Acids: A Coreflood Study

Sayed

Nasr‐El‐Din

2013

SPE Production and Operations Symposium

View full text Add to dashboard Cite

Acid treatments in deep wells drilled in carbonate reservoirs represent a challenge to the oil industry. Emulsified acid can be used in matrix acidizing and acid fracturing treatments. The delayed nature of emulsified acid is useful in creating deep wormholes and etched fracture surfaces. The high temperature of deep wells requires a special formulation of emulsified acid that is stable and effective at such high temperatures. The main objective of the present work is to study the performance of emulsified acid in stimulating high temperature deep wells drilled in dolomitic carbonate reservoirs.A coreflood study was conducted using dolomite cores, which had dimensions of 1.5 in. diameter and 6 in. length. The initial permeability of the dolomite cores used in the current study ranged from 1.6 to 20.9 md. Emulsified acid systems were formulated at 0.7 acid volume fraction, 1.0 vol% emulsifier, and 15 wt% HCl concentration. Coreflood experiments were performed at a temperature of 300°F, at injection rates range from 0.5 to 10 cm 3 /min until acid breakthrough the core. Samples of the effluent fluids were collected and analyzed using ICP to measure the calcium and magnesium concentrations. All cores were CAT scanned before acid treatment to study the presence of vugs, and after acid injection to study the characteristics of the generated wormhole.The results show that the emulsified acid created wormholes in dolomite cores, resulting in better treatment outcome. For emulsified acid injection rates in the range from 0.5 to 10 cm 3 /min, the volume of emulsified acid injected to achieve breakthrough increased with the increase in the emulsified acid injection rate. Also, there was no optimum injection rate for the injection rate range studied (0.5 to 10 cm 3 /min). The number and size of the created wormholes was function of the injection rate of emulsified acid. This paper summarizes the results obtained and recommends the use of emulsified acid systems for field applications with dolomite reservoirs.

show abstract

“…These alternatives include: organic acids (Harris 1961;Abrams et al 1983) such as acetic and formic acid, chemically retarded acids such as emulsified acid (Dill 1961;Knox et al 1964;Crenshaw and Flippen 1968;Nasr-El-Din et al 2001) and foamed acid (Bernadiner et al 1992), or viscosified acids like gelled acid (Pabley et al 1982;Deysarkar et al 1984;Crowe et al 1989) and in-situ gelled acid (Johnson et al 1988;Yeager and Shuchart 1997;Saxon et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Emulsified Chelating Agent: Evaluation of an Innovative Technique for High Temperature Stimulation Treatments

2013

View full text Add to dashboard Cite

Acid treatments in wells drilled in carbonate reservoirs aim to remove the damage, and increase the permeability in the area around the wellbore. Regular HCl used to be the main stimulation fluid; however at high temperatures, HCl causes excessive corrosion, rapid acid spending and face dissolution. For high temperature treatments, the alternatives are limited; including chelating agents, such as GLDA (glutamic acid-N,N-diacetic acid) and HEDTA (N-hydroxyethyl-ethylenediamine-triacetic acid).This paper discusses the evaluation of an innovative technique to formulate a new emulsified chelating agent that can be used for high temperature stimulation treatments. GLDA (pH = 3.8) of 38 wt% initial concentration was selected to formulate the emulsified GLDA (EGLDA). The EGLDA was formulated using a cationic emulsifier, with final GLDA concentration and volume fraction of 20 wt% and 0.7, respectively. The viscosity of the new EGLDA was measured at temperatures up to 300°F using an HPHT rheometer. The reaction of the EGLDA and limestone rock was studied using a rotating disk apparatus at temperature of 230°F. Coreflood experiments were performed using low permeability Indiana limestone core samples and emulsified GLDA at a temperature of 300°F and injection rate of 2.0 cm 3 /min.EGLDA is a non-Newtonian shear-thinning fluid, where the viscosity can be represented by the power-law model. The emulsified GLDA achieved a viscosity of 57.5 cp at 100 s -1 and 75°F. The EGLDA was stable up to 300°F, and the apparent viscosity at 10 s -1 shear was found to be 40 cp. The reaction rates of EGLDA with calcite were in the range of 6.2X10 -8 to 1.2X10 -7 gmole/cm 2 .s, less by 2 orders of magnitude than those of 15 wt% HCl emulsified acid formulated by 1.0 vol% emulsifier and reacted with calcite at a temperature of 230°F. The coreflood experiments performed using EGLDA and Indiana limestone cores, indicated that emulsified GLDA was able to enhance the permeability of the core by a factor of 3.7 times. From the work done, the EGLDA achieved low reaction rates with no face dissolution at high temperature, and this will results in better stimulation treatments, especially in high temperature wells. ConclusionsAn innovative technique of emulsifying the chelating agents was evaluated. Emulsified GLDA systems were formulated using a cationic emulsifier and 20 wt% GLDA solutions. The viscosity of the emulsified GLDA systems was examined under different emulsifier concentrations, and temperatures. Coreflood and reaction rate studies were performed to evaluate the performance of the emulsified GLDA. Based on the results obtained, the following conclusions can be drawn:1. The emulsified GLDA was a non-Newtonian shear thinning fluid.2. There was no significant effect of changing the emulsifier concentration on the apparent viscosity of emulsified GLDA. 3. From the coreflood study, the emulsified GLDA was able to enhance the permeability of Indiana limestone core samples by a factor of 3 to 3.7. 4. The emulsified GLDA was used effectively, with...

show abstract

Field Application of Emulsified Acid-Based System to Stimulate Deep, Sour Gas Reservoirs in Saudi Arabia

Abstract: TX 75083-3836, U.S.A., fax 01-972-952-9435. Abstract

Cited by 48 publications

References 9 publications

Combining Selective Stimulation With Tailored Perforating Improves Injection Profile in a Carbonate Reservoir: A Case Study

Combining Selective Stimulation With Tailored Perforating Improves Injection Profile in a Carbonate Reservoir: A Case Study

Acid Treatments in High Temperature Dolomitic Carbonate Reservoirs Using Emulsified Acids: A Coreflood Study

Emulsified Chelating Agent: Evaluation of an Innovative Technique for High Temperature Stimulation Treatments

Contact Info

Product

Resources

About