Study on the optimization of injection modes and injection parameters for natural gas in ultra-low permeability reservoir

Wang, Miao; Dong, Liang; Chen, Feiyu; Dong, Wenzhuo

doi:10.1016/j.egyr.2022.03.114

Cited by 3 publications

(2 citation statements)

References 8 publications

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“…The breakdown pressure declined by 14.2% when the perforation rotated from 60 degrees to 0 degrees. The overall trend of the breakdown pressure is consistent with the results of numerical simulation studies [37][38][39][40]. The ideal perforation orientation angle is zero, corresponding to the minimum breakdown pressure [41].…”

Section: Effect Of Acidizingsupporting

confidence: 86%

A New Experimental Method for Acid Pretreatment in Perforated Horizontal Wells: A Case Study of Mahu Conglomerate Reservoir

Jia,

Mou,

Wang

et al. 2023

Processes

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The Mahu Oilfield in Xinjiang, China, is the world’s largest conglomerate oilfield, with a daily output of more than 8000 tons. In the fracturing of perforated horizontal wells, the breakdown pressure is high, resulting in difficulties in their treatment. Acid pretreatment has been applied to reduce the breakdown pressure in the field, but with poor performance. Few studies have been conducted on how acid pretreatment affects the breakdown pressure under perforation conditions in the Mahu conglomerate reservoir. Also, existing fracturing or acid pretreatment experiments cannot simulate perforation well. Therefore, a new method was developed to make perforations by hydro jetting the fracturing specimens (300 mm × 300 mm × 300 mm) first. It can achieve specified perforation parameters, including the perforation angle, position, and length. Subsequently, true triaxial hydraulic fracturing experiments were conducted on the conglomerate specimens obtained from the Mahu area. The effects of the acid pretreatment on the fracture initiation and breakdown pressure were investigated by injecting the perforation section of the conglomerate using various acid systems. The study results showed that the perforation made by the new apparatus was extremely close to the perforation on-site. The acid pretreatment effectively dissolved minerals and could decrease the breakdown pressure down to 7.7 MPa. A combination of 6%HF + 10%HCl was recommended for the acid pretreatment in the Mahu conglomerate reservoir. A total of 60 min acid–rock contact time is necessary for sufficient rock dissolution. The mechanism of the acid pretreatment to decrease the breakdown pressure is that the rock dissolution by the acid reduces the rock tensile strength and increases the permeability. The raised permeability increases the fluid pressure of the reservoir near the wellbore so as to reduce the breakdown pressure of the formation. The research results provide technical support for reducing construction difficulty and optimizing parameters in the Mahu Oilfield.

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Section: Effect Of Acidizingsupporting

confidence: 86%

A New Experimental Method for Acid Pretreatment in Perforated Horizontal Wells: A Case Study of Mahu Conglomerate Reservoir

Jia,

Mou,

Wang

et al. 2023

Processes

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“…Wang et al [8] found an inverse correlation between the pressure to volume ratio of oil and water wells using an analytical method of injection to production balance. Li Nan et al [9] compared the pressure profiles of oil and water wells at different moments of advance water injection and explained the effects on formation pressure caused by different injection methods. Yu Kaichun [10] studied the reasonable bottomhole flow pressure and reasonable water injection volume of water injection according to the feasibility of advance water injection.…”

Section: Introductionmentioning

confidence: 99%

Pressure Calculation Method and Mechanism of Advance Water Injection in Ultra-low Permeability Reservoirs

Zhou,

Cao,

Zhang

et al. 2024

Preprint

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Advance water injection is one of the effective methods to alleviate the rapid decline of formation pressure in ultra-low permeability reservoirs, to establish an effective displacement system between oil and water wells, and to increase the production of wells. In order to make up for the influence of threshold pressure gradient and stress sensitivity which are not fully considered in the traditional advance water injection pressure calculation model, based on the material balance method, threshold pressure gradient and stress sensitivity equations are introduced, a nonlinear flow model of the relationship between the advance water injection volume and formation pressure is established, and an iterative solution calculation program is compiled. Taking Y2 ultra-low permeability reservoir in Changqing Oilfield, China, as an example, the formation pressure values under different amounts of advance water injection in the well group of this block are calculated and compared with the numerical simulation results, which are basically in agreement with each other, proving that the model for calculating the advance water injection pressure established in this paper has a high calculation accuracy. The pressure and pressure gradient distribution law in the reservoir under different advance water injection volume is further revealed. When the advance water injection volume of the well group is greater than 10,000m 3 , the pressure lift becomes slower, and the pressure gradient between the oil and water wells is higher than the threshold pressure gradient, which forms an effective displacement system. The study results can provide theoretical guidance for the development of advance water injection technical programs for ultra-low permeability reservoirs.

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Quantitative evaluation of water-alternative-natural gas flooding in enhancing oil recovery of fractured tight cores by NMR

Liu,

Yao,

Liu

et al. 2023

J Petrol Explor Prod Technol

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As the associated gas of tight reservoirs, natural gas is abundant and noncorrosive, which is more suitable for the development of tight oil reservoirs in China. However, the mechanism of gas injection development is unclear, and the gas channeling is serious in tight reservoirs after fracturing. The water-alternating-gas (WAG) flooding is an effective means to delay gas channeling and improve oil recovery. Therefore, it is significant to clarify the mechanism of preventing gas channeling and recovering oil by water-alternation-natural gas (WANG) flooding. The WANG flooding experiments with different water–gas slugs were conducted in non-fracture and fractured tight cores. Besides, the oil distribution of different pore spaces of cores before and after displacement and the main contribution spaces on oil recovery were quantitatively analyzed by using nuclear magnetic resonance and core mercury porosimetry techniques. The results indicate that compared with natural gas flooding, the WANG flooding can retard gas channeling, increase formation energy, and enhance oil recovery by up to 14.1%, especially in fractured cores. Under the resistance of water slugs, the gas was allowed to enter smaller pores and its swept volume was expanded. Oil is mainly stored in mesopores (0.1–1 μm) and small pores (0.01–0.1 μm), accounting for over 90% of the total volume. The oil recovered mainly comes from mesopores, which accounts for over 75% of the total amount. Moreover, the WANG flooding strengthens the recovery of oil in mesopores and macropores (1–10 μm), but it also squeezes oil into small pores and micropores (0.001–0.01 μm).

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Study on the optimization of injection modes and injection parameters for natural gas in ultra-low permeability reservoir

Cited by 3 publications

References 8 publications

A New Experimental Method for Acid Pretreatment in Perforated Horizontal Wells: A Case Study of Mahu Conglomerate Reservoir

A New Experimental Method for Acid Pretreatment in Perforated Horizontal Wells: A Case Study of Mahu Conglomerate Reservoir

Pressure Calculation Method and Mechanism of Advance Water Injection in Ultra-low Permeability Reservoirs

Quantitative evaluation of water-alternative-natural gas flooding in enhancing oil recovery of fractured tight cores by NMR

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