A New Multichelating Acid System for High-Temperature Sandstone Reservoirs

Li, Nianyin; Zhang, Qian; Wang, Yongqing; Liu, Pingli; Zhao, Liqiang

doi:10.1155/2015/594913

Cited by 11 publications

(6 citation statements)

References 17 publications

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“…In petroleum industry, matrix acidizing has been employed to remove formation damage caused by drilling, workover, or production process and to enhance the formation permeability [1,2]. Mud acid has been extensively applied in matrix acidizing, which is composed of HCl and HF acid with different concentrations.…”

Section: Introductionmentioning

confidence: 99%

A High Effective Acid System to Stimulate Sandstone Reservoirs

2022

Geofluids

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Mud acid is regularly applied to recover or increase permeability of sandstone reservoir. However, due to its rapid reacting rate and heterogeneous displacement, the stimulation effect of conventional mud acid is relatively limited in sandstone formations. For mud acid, it is important to choose proper chemical additives to retard reaction rate and make it distributed homogenereously in formation. To overcome these shortcomings of mud acid, a new proprietary mud acid system has been developed for sandstone formations stimulation. The new system is composed of 2.0% multichemical solutions (MCS) +6.5%HCl+1.5% HF, and the combined solution contains nonionic surfactant, clay stabilizer, and dispersant which were specifically formulated. Core flooding experiments were conducted with the high effective mud acid; meanwhile, XRD and SEM analysis were performed before/after the core flooding tests. Retarded tests were also conducted for the new mud acid reacting with sandstone samples. Treatments with ten pores volume of the new high effective mud acid system were found to increase permeability of sandstone core approximately three times of its initial permeability. From the results of SEM and XRD analysis, most of clays were dissolved, and permeability was increased after core flooding by this new mud acid solution. On the basis of acidizing theory, the reaction retarded mechanism was explained about the new composite mud acid. Other properties of the new composite mud acid were also discussed. In comparison of conventional mud acid, the new composite mud acid can retard acidizing reaction rate and distribute evenly in formation; therefore, it can extend acidizing penetration and stimulate sandstone formation thoroughly. The new composite mud acid is more compatible and desirable than conventional mud acid, and it will be applied extensively for sandstone matrix stimulation.

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Section: Introductionmentioning

confidence: 99%

A High Effective Acid System to Stimulate Sandstone Reservoirs

2022

Geofluids

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“…To overcome the problems of conventional mud acid in high-temperature sandstone reservoirs, many attempts have been made from acid systems (Li et al 2015;Shafiq et al 2013;Zhou 2013;Mahmoud et al 2011;Thomas et al 2001;Gdanski 1985). One of these attempts was to develop retarded mud acid systems.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of one-step economical retarded sandstone acid

Yang

2021

J Petrol Explor Prod Technol

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The objective of this study is to experimentally evaluate a new acid combination of HEDP: CH3COOH as a retarded acid to minimize some limitations of high-temperature sandstone acidizing, such as fast acid-rock reaction and secondary precipitation pipeline corrosion. In this work, the acid–base titration, core-powder solubility test, scale deposition test, corrosion rate measurement and corefloods were carried out to evaluate the performances of the acid combination, including acidity characteristics, retarded performance, preventing scale rate, corrosivity and improving permeability. And then the microstructure and mineral content in sandstone samples were observed and analyzed with SEM–EDS. The results of evaluation tests indicated that the new acid combination has excellent performances on retarded rate, preventing scale deposition, permeability enhancement and lower corrosivity, comparing with conventional mud acid. The results of SEM and EDS showed that the microstructure and mineral content of sandstone changed after acid treatment. Compared with mud acid, the new acid system can react more with small particles on sandstone surface and less with the skeleton of samples and the decrease in the contents of Mg, Al, Na, K, Ca and Fe is relatively lower.

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“…The amount of AlF 3 precipitated was a strong function of the Al/F ratio in the solution. Li et al introduced a new acid system that consists of a combination of chelating agents, phosphoric acid (H 3 PO 4 ), and NH 4 F for high-temperature applications for sandstone reservoirs. The new acid system has a low corrosion rate and prevented the precipitation of CaF 2 .…”

Section: Introductionmentioning

confidence: 99%

Novel Approach for Sandstone Acidizing Using in Situ-Generated Hydrofluoric Acid with the Aid of Thermochemicals

2020

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In this study, an in situ-generated hydrofluoric acid (HF) was used for sandstone acidizing, where an acid precursor (ammonium fluoride NH 4 F) reacted with a suitable oxidizer (sodium bromates NaBrO 3 ) in an exothermic reaction. First, the new chemical mixture was prepared to react with pure quartz samples and the reaction effluent was analyzed to identify the presence of Si + ions using the inductively coupled plasma (ICP) technique. Core flooding experiments were performed using Gray Berea sandstone cores (6 in. length and 1.5 in. diameter). A preflush stage of 5 PV of 7 wt % HCl was injected to remove any calcite content in the core. The main chemicals were then flushed for 3 successive cycles of 1 PV each. To assure core integrity, scratch tests and NMR scans were run on the core sample before and after the treatment. The new chemical mixture could dissolve the quartz sample and reduce its weight by 80 mg. The concentration of the dissolved Si + ions was more than 90 ppm. This proves the capability of the chemical mixture to generate HF. The initial core permeability was measured at a stabilized flow rate of 2 cm 3 /min to be 33 mD. After the acid preflush stage, the core permeability reduced to 31 mD. Core permeability increased immediately after the first treatment cycle and reached 41 mD. At the end, the core flooding results showed a permeability improvement for Gray Berea sandstone cores by almost 40%. The ICP analysis of the effluent showed a total amount of chelated Si + ions of about 10.5 mg. In addition to the high temperature generated in the near-wellbore area, the pressure increased because of the produced nitrogen gas from the exothermic reaction and reached about 600 psi. The scratch test showed an increase in the sample uniaxial compressive strength from 7432 to 9235 psi. The dynamic Poisson's ratio and the dynamic Young's modulus increased as well from 0.17 to 0.19 and from 2159 to 3585 ksi, respectively. The enhancement in the mechanical properties of the core can be attributed to the presence of the potassium element in Berea cores and its solidification reaction with the HF generated. The NMR measurements of the core sample before and after the acidizing process show an increase in the core porosity; however, the core preserved its original pore system. Upon application of this new stimulation technology, the true production potential of sandstone reservoirs can be achieved, well tubular corrosion will be minimized, and handling hazardous chemicals such as HF will be avoided. Most importantly, controlling the reaction rate, by controlling the amount of exothermic chemicals, can ensure deep acid penetration as well.

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A New Multichelating Acid System for High-Temperature Sandstone Reservoirs

Cited by 11 publications

References 17 publications

A High Effective Acid System to Stimulate Sandstone Reservoirs

A High Effective Acid System to Stimulate Sandstone Reservoirs

Experimental study of one-step economical retarded sandstone acid

Novel Approach for Sandstone Acidizing Using in Situ-Generated Hydrofluoric Acid with the Aid of Thermochemicals

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