Progress and development directions of stimulation techniques for ultra-deep oil and gas reservoirs

Lei, Qun; Xu, Yizhuang; Yang, Zhanwei; Chen, Bo; Wang, Xin; Zhou, Lei; Liu, Huifeng; Xu, Minjie; Wang, Liwei; Li, Shuai

doi:10.1016/s1876-3804(21)60018-6

Cited by 89 publications

(23 citation statements)

References 17 publications

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“…Reasonable fracture spacing can reduce unnecessary packers and mutual interference between acid fracturing fractures. Reducing the fracture spacing is conducive to expanding the drainage area of gas wells, but the research shows that, when the fracture spacing is shortened to a certain extent, the productivity of gas wells will not be significantly improved, and there is an economic optimal fracture spacing for staged acid fracturing of horizontal wells [ 50 , 51 , 52 , 53 ]. According to the reservoir porosity, permeability, gas saturation, and other physical parameters in the Sichuan Basin, we used Eclipse to establish the numerical simulation model of staged acid fracturing horizontal wells in carbonate gas reservoirs, and the relevant parameters selected in the model are shown in Table 1 .…”

Section: Resultsmentioning

confidence: 99%

A New Compound Staged Gelling Acid Fracturing Method for Ultra-Deep Horizontal Wells

Wang¹,

Fan²,

Wang

et al. 2022

Gels

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Carbonate gas reservoirs in Sichuan are deeply buried, high temperature and strong heterogeneity. Staged acid fracturing is an effective means to improve production. Staged acidizing fracturing of ultra-deep horizontal wells faces the following problems: 1. Strong reservoir heterogeneity leads to the difficulty of fine segmentation; 2. The horizontal well section is long and running too many packers increases the completion risk; 3. Under high temperatures, the reaction speed between acid and rock is rapid and the acid action distance is short; and 4. The fracture conductivity is low under high-closure stress. In view of the above problems, the optimal fracture spacing is determined through productivity simulation. The composite temporary plugging of fibers and particles can increase the plugging layer pressure to 17.9 MPa, which can meet the requirements of the staged acid fracturing of horizontal wells. Through the gelling acid finger characteristic simulation and conductivity test, it is clear that the crosslinked authigenic acid and gelling acid in the Sichuan carbonate gas reservoir are injected alternately in three stages. When the proportion of gelling acid injected into a single section is 75% and the acid strength is 1.6 m3/m, the length and conductivity of acid corrosion fracture are the best. A total of 12 staged acid fracturing horizontal wells have been completed in the Sichuan carbonate gas reservoir, and the production is 2.1 times that of ordinary acid fracturing horizontal wells.

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Section: Resultsmentioning

confidence: 99%

A New Compound Staged Gelling Acid Fracturing Method for Ultra-Deep Horizontal Wells

Wang¹,

Fan²,

Wang

et al. 2022

Gels

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“…With the development of the petroleum industry and the consumption of shallow oil resources, oil and gas exploration has been gradually forced to transit from shallow reservoirs to deep strata, which creates a technical challenge for deep well drilling operations [ 1 , 2 , 3 ]. The drilling fluid in the drilling process of oil and gas wells can be seen as the equivalent of the blood in the human body, and high-temperature and high-density drilling fluid plays an important role in the whole deep well drilling operation.…”

Section: Introductionmentioning

confidence: 99%

Study of a High-Temperature and High-Density Water-Based Drilling Fluid System Based on Non-sulfonated Plant Polymers

You

Zhou

2022

Polymers

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The environment-friendly water-based drilling fluid system developed for the petroleum development industry cannot successfully withstand temperatures up to 180 °C, and most high temperature-resistant additives with sulfonic acid groups that have been successfully applied to water-based drilling fluid are not good for environmental protection. In order to solve the above technical problems, a non-sulfonated filtrate reducer and viscosity reducer with resistance to high temperature were prepared by using humic acid, lignin and a multifunctional monomer as raw materials. In laboratory experiments, the molecular weights of the FLO-H filtrate reducer and the VR-H viscosity reducer were 5.45 × 105 g/mol and 8.51 × 103 g/mol, respectively, and all of them showed good high-temperature resistance. The API filtration loss of the bentonite-base slurry with 3.0 wt% FLO-H was only 6.2 mL, which indicated that FLO-H had a prominent reduction in filtration loss after aging at high temperature. When the dosage of VR-H was 1.0 wt%, the plastic viscosity of the water-based drilling fluid after aging at 200 °C decreased from 71 mPa·s to 55 mPa·s, which provided excellent dispersion and dilution. The high-temperature and high-density water-based drilling fluid containing the FLO-H filtrate reducer and the VR-H viscosity reducer had good suspension stability and low filtration performance at the high temperature of 200 °C, which can meet the requirements of high-temperature deep well drilling.

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“…The exploration and development of ultra-deep natural gas reservoirs are faced with the complex environments of high temperature, high pressure and high in situ stress, and there exist the complex multiphysics-coupled processes of the fluid flow between the reservoir and the wellbore (Selvadurai et al 2018;Lei et al 2021). The mechanical deformation due to the changes of fluid pressure in reservoirs is an important aspect that should be considered in the reservoir depletion (Sangnimnuan et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Multiphysics coupling study of near-wellbore and reservoir models in ultra-deep natural gas reservoirs

Cheng

Shen

et al. 2022

J Petrol Explor Prod Technol

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Understanding the changes of the near-wellbore pore pressure associated with the reservoir depletion is greatly significant for the development of ultra-deep natural gas reservoirs. However, there is still a great challenge for the fluid flow and geomechanics in the reservoir depletion. In this study, a fully coupled model was developed to simulate the near-wellbore and reservoir physics caused by pore pressure in ultra-deep natural gas reservoirs. The stress-dependent porosity and permeability models as well as geomechanics deformation induced by pore pressure were considered in this model, and the COMSOL Multiphysics was used to implement and solve the problem. The numerical model was validated by the reservoir depletion from Dabei gas field in China, and the effects of reservoir properties and production parameters on gas production, near-wellbore pore pressure and permeability evolution were discussed. The results show that the gas production rate increases nonlinearly with the increase in porosity, permeability and Young’s modulus. The lower reservoir porosity will result in the greater near-wellbore pore pressure and the larger rock deformation. The permeability changes have little effect on geomechanics deformation while it affects greatly the gas production rate in the reservoir depletion. With the increase in the gas production rate, the near-wellbore pore pressure and permeability decrease rapidly and tend to balance with time. The reservoir rocks with higher deformation capacity will cause the greater near-wellbore pore pressure.

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Progress and development directions of stimulation techniques for ultra-deep oil and gas reservoirs

Cited by 89 publications

References 17 publications

A New Compound Staged Gelling Acid Fracturing Method for Ultra-Deep Horizontal Wells

A New Compound Staged Gelling Acid Fracturing Method for Ultra-Deep Horizontal Wells

Study of a High-Temperature and High-Density Water-Based Drilling Fluid System Based on Non-sulfonated Plant Polymers

Multiphysics coupling study of near-wellbore and reservoir models in ultra-deep natural gas reservoirs

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