An experimental investigation of fracturing fluids on physico-mechanical damage properties of carbonates in block Shunbei

ABSTRACT

For the purpose of revealing the effect of fracturing fluids on rock breaking, wellbore stability, and fracturing reformation. A multi-scale evaluation method is initially established in the paper by analyzing and investigating based on laboratory experiment of different fracturing fluids on Physico-mechanical Damage Properties of Carbonates. This paper has taken carbonate reservoir of block Shunbei in Xinjiang as the research object, the influence of different fracturing fluids on physico-mechanical properties and damage mechanism has been deeply studied by microanalysis, laboratory physical and mechanical tests and theoretical analysis. The results show that gelled acid has a remarkable time-effect on the deterioration of physical and mechanical properties of the carbonate samples, and the optimal degradation time is 30 min. The impact degree of three fracturing fluids is discrepant, and the damage effect of gelled acid is more significant than that of cross-linked acid and slickwater, for physical properties and micro-composition have the largest attenuation, and the spacing between mineral crystals increase, with the arrangement becoming looser. For mechanical damage characteristics, the deterioration and attenuation of rock mechanical properties including rock compressive, tensile and shear strength are significant, and the failure mode changes from a single fracture to multiple fractures. The mechanism on the physico-mechanical damage characteristics of carbonate rock is mainly caused by the physical deterioration, chemical erosion, and mechanical damage. In summary, based on the degradation effect and influence degree of the three fracturing fluids on the carbonates, their effects are as: gelled acid > cross-linked acid > slickwater, so gelled acid is more suitable as a fracturing fluid for a carbonate reservoir to enhance the complexity of crack propagation and achieve maximum volume of stimulation.

KEYWORDS:

• Mechanical damage
• carbonate rock
• fracturing fluid
• physical deterioration
• Shunbei oilfield

Additional information

Funding

This research was supported by the National Key R&D Program of China(No.2018YFC1504903), the National Natural Science Foundation of China (No. 51574218), the National Science and Technology Major Project (Nos. 2016ZX05060017, 2017ZX05036003004), the Strategic Priority Research Program of Chinese Academy of Sciences (No. XDB10040200).

Notes on contributors

Peng Deng

Peng Deng, Master of Chongqing University, Ph.D. of Harbin Institute of Technology,  mainly engaged in the research and utilization of unconventional oil and gas efficient developments.

Yintong Guo

Yintong Guo, Professor in Chinese Academy of Sciences, mainly engaged in the study of rock mechanical properties and fracturing reformation inOil and gas field.

Jun Zhou

Jun Zhou, Ph.D. of University of Chinese Academy of Sciences, mainly engaged in the research of rock mechanics in petroleum engineering.

Lei Wang

Lei Wang, Ph.D. of Chinese Academy of Sciences, mainly engaged in hydraulic fracturing mechanics of shale gas.

Xiaogui Zhou

Xiaogui Zhou, Master of Kunming University of Science and Technology, mainly engaged in the brittleness evaluation of shale mechanical properties.

Feng Xu

Feng Xu, Ph.D. in China Merchants Chongqing Communications Research & Design Institute Co., Ltd, mainly engaged in geotechnical and engineering research.