Equilibrium Acid Fracturing: A New Fracture Acidizing Technique for Carbonate Formations

1991 ◽  
Vol 6 (01) ◽  
pp. 25-32 ◽  
Author(s):  
S.J. Tinker
Keyword(s):  
Acid Fracturing ◽  
Carbonate Formations

Study on Acid Fracturing Technology for Carbonate Reservoirs in Ordos Basin

2020 ◽  
Author(s):  
Mu Li ◽  
Lufeng Zhang ◽  
Minghui Li
Keyword(s):  
Ordos Basin ◽  
Natural Fracture ◽  
Deep Penetration ◽  
Acid Rock ◽  
Acid Fracturing ◽  
Fracture Length ◽  
Two Parameters ◽  
Carbonate Formations ◽  
Microstructure Characteristic ◽  
Mechanics Characteristics

Abstract Acid fracturing, a key stimulation technology, has been widely applied in carbonate formations, which have the complex reservoir space and natural fracture. However, the conventional acid fracturing technology has limitations in target reservoir due to serious acid leakage and rapid acid-rock reaction speed. Therefore, a deep-penetration acid fracturing technology was proposed to enhance the stimulation effect. The reservoir basic physical properties, such as permeability and porosity, microstructure characteristic of pore throats, mineral composition, and rock mechanics characteristics, were systemically investigated by a series of laboratory experiments. The acid system was also optimized by evaluating rheological properties and residual acid damage. Furthermore, the most important two parameters of acid fracturing, conductivity and effective acid-etched fracture length, were obtained by numerical simulation with commercial software Fracpro PT. Based on the laboratory studies, the acid fracturing technology was applied in the field, and the production of well increased by 1.7 times after stimulation.

The Evaluation and Introduction of Novel Acid-Based Crosslinked Gel for HPHT Acid Fracturing Applications in Carbonate Formations

2022 ◽  
Author(s):  
Khalid Fahad Almulhem ◽  
Ataur Malik ◽  
Mustafa Ghazwi
Keyword(s):  
Traditional Approach ◽  
Reaction Rates ◽  
Field Trials ◽  
Gas Production ◽  
Carbonate Reservoir ◽  
Fluid System ◽  
Acid Fracturing ◽  
Acid Reaction ◽  
Carbonate Formations

Abstract Acid Fracturing has been one of the most effective stimulation technique applied in the carbonate formations to enhance oil and gas production. The traditional approach to stimulate the carbonate reservoir has been to pump crosslinked gel and acid blends such as plain 28% HCL, emulsified acid (EA) and in-situ gelled acid at fracture rates in order to maximize stimulated reservoir volume with desired conductivity. With the common challenges encountered in fracturing carbonate formations, including high leak-off and fast acid reaction rates, the conventional practice of acid fracturing involves complex pumping schemes of pad, acid and viscous diverter fluid cycles to achieve fracture length and conductivity targets. A new generation of Acid-Based Crosslinked (ABC) fluid system has been deployed to stimulate high temperature carbonate formations in three separate field trials aiming to provide rock-breaking viscosity, acid retardation and effective leak-off control. The ABC fluid system has been progressively introduced, initially starting as diverter / leak off control cycles of pad and acid stages. Later it was used as main acid-based fluid system for enhancing live acid penetration, diverting and reducing leakoff as well as keeping the rock open during hydraulic fracturing operation. Unlike in-situ crosslinked acid based system that uses acid reaction by products to start crosslinking process, the ABC fluid system uses a unique crosslinker/breaker combination independent of acid reaction. The system is prepared with 20% hydrochloric acid and an acrylamide polymer along with zirconium metal for delayed crosslinking in unspent acid. The ABC fluid system is aimed to reduced three fluid requirements to one by eliminating the need for an intricate pumping schedule that otherwise would include: a non-acid fracturing pad stage to breakdown the formation and generate the targeted fracture geometry; a retarded emulsified acid system to achieve deep penetrating, differently etched fractures, and a self-diverting agent to minimize fluid leak-off. This paper describes all efforts behind the introduction of this novel Acid-Based Crossliked fluid system in different field trials. Details of the fluid design optimization are included to illustrate how a single system can replace the need for multiple fluids. The ABC fluid was formulated to meet challenging bottom-hole formation conditions that resulted in encouraging post treatment well performance.

scholarly journals Case study of acid fracturing of Ordovician geothermal reservoir in Taiyun area

2021 ◽  
Vol 300 ◽  
pp. 01002
Author(s):  
Xingwu Feng ◽  
Ruohan Hu ◽  
Degang Xing ◽  
Qingzhong Yu ◽  
Jiawei Chen ◽  
...  
Keyword(s):  
Experimental Tests ◽  
Hot Water ◽  
Geothermal Reservoir ◽  
Water Production ◽  
Fracture Width ◽  
Acid Fracturing ◽  
Fracture Length ◽  
Multi Stage ◽  
Resistance Reduction ◽  
Carbonate Formations

The thermal reservoir in Taiyun area mainly consists of Ordovician and Cambrian carbonate formations. The target interval of example well contains more than 95% carbonate, being thick, argilliferous and have well-developed natural fissures and rich hot water. However, sometimes stimulation is necessary to achieve the designed water production rate. In this paper, multistage alternating injection acid fracturing technology is selected according to lithologic characteristics of geothermal reservoir. A gel acid, which is a composite of 20%HCl+0.8%SHY1+2% corrosion inhibitor+1.5% iron ion stabilizer+1% cleanup additive, is optimized and developed by experimental tests. Its viscosity can reach 27 mPa·s. Then, pumping schedule of multi-stage alternate injection acid fracturing is optimized by numerical simulator of acid fracturing design. It is shown from job pressure of field sample well that resistance reduction ability of gel acid needs to be further improved. Moreover, from the analysis results of pressure decline after acid fracturing, the fluid efficiency is 42.32%, net pressure is 3.3 MPa, and the dynamic fracture length is 107m, the maximum fracture width is 8.6mm by fitting treatment pressure. The water production increase factor reaches 1.2 after acid fracturing treatment. Therefore, the acid fracturing treatment is successful.

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