Successful Application of Novel Modified HF Acid System for Sandstone Matrix Acidizing in B Field

2019 ◽  
Author(s):  
Chang Siong Ting ◽  
Zayful Kamarudzaman ◽  
M Ikhwan Aris ◽  
Nurul Ezween Hasbi ◽  
Suzanna Juyanty M Jeffry ◽  
...  
Keyword(s):  
Acid System ◽  
Matrix Acidizing

Experimental Evaluation of a New Nonaromatic Nonionic Surfactant for Deep Carbonate Stimulation

2021 ◽  
pp. 1-12
Author(s):  
Khatere Sokhanvarian ◽  
Cornell Stanciu ◽  
Jorge M. Fernandez ◽  
Ahmed Farid Ibrahim ◽  
Harish Kumar ◽  
...  
Keyword(s):  
Nonionic Surfactant ◽  
Pore Volume ◽  
Inductively Coupled Plasma ◽  
Oil And Gas ◽  
Low Cost ◽  
Acid System ◽  
Matrix Acidizing ◽  
High Corrosion ◽  
First Choice ◽  
The Stability

Summary Matrix acidizing improves productivity in oil and gas wells. Hydrochloric acid (HCl), because of its many advantages such as its effectiveness, availability, and low cost, has been a typical first-choice fluid for acidizing operations. However, HCl in high-pressure/high-temperature (HP/HT) wells can be problematic because of its high reactivity, resulting in face dissolution, high corrosion rates, and high corrosion inhibition costs. Several alternatives to HCl have been tested; among them, emulsified acid is a favorable choice because of its inherent low corrosion rate, deeper penetration into the reservoir, fewer asphaltene/sludge problems, and better acid distribution due to its higher viscosity. The success of the new system is dependent upon the stability of the emulsion, especially at high temperatures. The emulsified acid must be stable until it is properly placed, and it must also be compatible with other additives in an acidizing package. This study develops a stable, emulsified acid system at 300°F using aliphatic nonionic surfactants. This paper introduces a new nonaromatic, nonionic surfactant to form an emulsified acid for HP/HT wells. The type and quality of the emulsified acid were assessed through conductivity measurements and drop tests. The thermal stability of the system was monitored as a function of time through the use of pressure tubes and a preheated oil bath at 300°F. A LUMisizer® (LUM GmbH, Berlin, Germany) and Turbiscan® (Formulaction, S. A., L’Union, France) were used to determine the stability and the average droplet size of the emulsion, respectively. The viscosity of the emulsified acid was measured at different temperatures up to 300°F as a function of shear rate (1 to 1,000 s−1). The microscopy study was used to examine the shape and the distribution of acid droplets in diesel. Coreflood studies at low and high flow rates were conducted to determine the performance of the newly developed stable emulsified acid in creating wormholes in carbonate rocks. Inductively coupled plasma and computed tomography (CT) scans were used to determine the dissolved cations and wormhole propagation, respectively. Superior stimulation results with a low pore volume of acid to breakthrough (PVBT) were achieved at 300°F with the newly developed emulsified acid system. The wormhole propagation was narrow and dominant compared to branched wormholes resulting from conventional emulsified acid systems. Results indicate that a nonionic surfactant with optimal chemistry, such as a suitable hydrophobe chain length and structure, can form a stable emulsified acid. In this study we introduce a new and effective aliphatic nonionic surfactant to create a stable emulsified acid system for matrix acidizing at HP/HT conditions, leading to a deeper penetration of acid with low pore volume to breakthrough. The successful core flood studies in the laboratory using carbonate cores suggest that the new emulsified acid system may efficiently stimulate HP/HT carbonate reservoirs.

The Feasibility of Fluorine Ammonium Compounds for Sandstone Formation Matrix Acidizing: Laboratory Study and Discussion

2013 ◽  
Vol 773 ◽  
pp. 628-633
Author(s):  
Fu Li ◽  
An Lin Wu ◽  
Min Min Xia ◽  
Hong Xian Liu ◽  
Ting Ting Zhang
Keyword(s):  
Acid System ◽  
Matrix Acidizing ◽  
Chemical Structures ◽  
Well Stimulation ◽  
Energy Needs ◽  
Ammonium Hydrogen ◽  
Lower Effect ◽  
Sandstone Formation ◽  
Great Possibility ◽  
Ammonium Compounds

As a preferred technology to enhance oilfield energy production, well stimulation has and will continue to have an important role in fulfilling the worlds future energy needs. Mud acid is a conventional acid system that reacts with most injurants and removes damages. However, fast reaction rate with minerals will lead to high leak-off velocity, great possibility of secondary and tertiary precipitation, lower effect of corrosion inhibitor in high temperature as well as short efficient operating range. Therefore, new kinds of acid system are required to cope with these problems above. This paper proposed three acid system with the similarity of fluorine ammonium compounds for sandstone acidizing ammonium hydrogen fluoride (AHF), ammonium fluotitanate (AFT), and ammonium fluoroborate system (AFB). Chemical structures, acidity test and solubility tests have proved the feasibility. Then, performance comparisons are conducted to prove the advantages over mud acid system.

Addressing Matrix Acidizing Stimulation Challenges in Depleted, High-Temperature, and Acid-Sensitive Sandstone Formations with a High-Performance Acid System

2021 ◽  
Author(s):  
Rao Shafin Khan ◽  
Nestor Molero ◽  
Philippe Enkababian ◽  
Aizaz Khalid ◽  
Malik Anzar Afzal ◽  
...  
Keyword(s):  
High Temperature ◽  
Organic Acid ◽  
High Performance ◽  
Clay Content ◽  
High Energy ◽  
Acid System ◽  
Matrix Acidizing ◽  
Well Production ◽  
Production Trend ◽  
Sandstone Reservoirs

Abstract Acid stimulation in high-temperature sandstone reservoirs with high clay content can lead to undesired results due to secondary and tertiary reactions between treatment fluids and reservoir clays. Although there have been significant advancements in treating clastic formations over the years, high bottomhole temperature (BHT) coupled with high clay content of up to 35% and subhydrostatic conditions still presents a major challenge. A stimulation workflow to address these challenges was adapted to treat and successfully enhance well production in sandstone reservoirs in southern Pakistan. Candidate wells were selected for acidizing treatments based on declining production trend and identification of significant damage skin. X-ray diffraction tests on core samples indicated presence of acid-sensitive clays and calcite. Due to the risk of precipitation from secondary and tertiary reactions, conventional hydrochloric and hydrofluoric acid treatments were not viable options. Core flow testing was conducted to assess the efficiency of alternative acid systems at the reservoir conditions with BHT above 320°F, validating the selection of a high-performance sandstone acid system that was designed to handle undissolved clays in the critical matrix by helping to bind the clays to the pore surfaces, thus preventing them from migrating and plugging the pore throat during flowback. The matrix stimulation campaign included vertical and deviated dry gas wells, completed with 3 1/2-in. to 4 1/2-in. production tubing and 7-in. liner, with perforated intervals averaging 20 ft. Prior to the main acid treatment, high-pressure rotary jetting across the target intervals was conducted by pumping organic acid via coiled tubing. This wellbore conditioning technique allowed maximizing the acid performance by delivering 360° high-energy fluid to clear the perforations of scale and improve injectivity. The main treatment consisted of an organic acid preflush and a high-performance sandstone acid system as the main fluid, followed by a brine post-flush. Throughout the treatment, nitrogen was added to all fluids to facilitate fluid flowback under subhydrostatic conditions. The wells treated using this matrix stimulation engineered workflow yielded sustained production gains from 3 MMscf/D to 3.5 MMscf/D, exceeding expectations by more than 50% and achieving payback periods less than 20 days. The success of the treatment was largely due to the carefully designed stimulation workflow and its flawless execution. Acidizing high-temperature sandstone reservoirs with 30 to 35% clay content is uncommon. The experience gained in southern Pakistan validates the high-performance sandstone acid system as a reliable option for matrix acidizing in hot, acid-sensitive sandstone reservoirs. It also provides a detailed engineering workflow for candidate selection, treatment design, and job execution and evaluation, which can easily be adapted to regions facing similar challenges.

Understanding Diversion with a Novel Fiber-Laden Acid System for Matrix Acidizing of Carbonate Formations

2010 ◽  
Author(s):  
Charles Edouard Cohen ◽  
Philippe Michel Jacques Tardy ◽  
Timothy Michael Lesko ◽  
Bruno H. Lecerf ◽  
Svetlana Pavlova ◽  
...  
Keyword(s):  
Acid System ◽  
Matrix Acidizing ◽  
Carbonate Formations

A Novel Polymer-Assisted Emulsified-Acid System Improves the Efficiency of Carbonate Matrix Acidizing

SPE Journal ◽  
2016 ◽  
Vol 21 (03) ◽  
pp. 1061-1074 ◽  
Author(s):  
A. S. Zakaria ◽  
H. A. Nasr-El-Din
Keyword(s):  
Polymer Concentration ◽  
Volume Ratio ◽  
High Viscosity ◽  
Low Permeability ◽  
Acid System ◽  
Matrix Acidizing ◽  
Viscosity Measurements ◽  
Internal Phase ◽  
Acid Diversion ◽  
Injection Rates

Summary In highly heterogeneous carbonate reservoirs, several acid systems were used to enhance acid diversion during matrix-acidizing treatments. Viscosified acid with polymer increases the viscosity of the acid system to improve the wellbore coverage. However, the injection of such acid at low rates had a negative effect on the spending rate and starts filter-cake formation, which inhibits the wormhole growth. On the other hand, relatively low-viscosity emulsified acid is diffusion-retarded, which makes it an effective wormholing agent at the low injection rates that occur, for example, in low-permeability or damaged formations. None of the studies in the literature addresses an acid system that uses both advantages. The objective of this work was to investigate the behavior and the performance of a new acid system, polymer-assisted emulsified acid, as a self-diverting acid by conducting viscosity measurements through coreflood study and acid-diversion experiments. The system was 15 wt% hydrochloric acid (HCl)-gelled acid emulsified in diesel with a 70:30 acid/diesel volume ratio. Coreflood experiments with Indiana limestone were conducted at 230°F at different injection rates, and the core samples were imaged with a computed-tomography (CT) scan technique after each coreflood experiment. Also, 0.5 pore volumes (PV) of the polymer-assisted emulsified acid was injected to assess the effect of the acid on the permeability of the cores before breakthrough. Finally, two acid-diversion experiments at 1 cm3/min were conducted into pairs of low- and high-permeability cores to test the effect of polymer concentration in the acid internal phase on diversion. The viscosity measurements and acid-diffusivity measurements showed that increasing the polymer concentration in the acid internal phase of the emulsified acid from 0 to 1.5 vol% significantly enhanced the viscosity of the emulsified acid and reduced the diffusion coefficient by one order of magnitude. Coreflood results showed that the polymer-assisted emulsified acid was an effective wormholing fluid at low injection rates while maintaining the high viscosity of the acid system for zonal coverage. Also, it was shown that the emulsion/polymer retention was the main source for permeability damage. However, flowback with mutual solvent removed any remaining damage, and permeability enhancement was achieved. Acid-diversion experiments are presented that show the self-diverting ability of the polymer-assisted emulsified acid into the low-permeability cores.

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