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Investigation of rheological behavior, filtration characteristics and microbial activity of biopolymer water-based drilling fluids containing monovalent and divalent cations

Shaine Mohammadali Lalji, Syed Imran Ali, Muhammad Arqam Khan, and Rizwan Ghauri

Department of Petroleum Engineering, NED University of Engineering and Technology, Karachi, Pakistan

Received: 2 February 2023 Accepted: 4 April 2023

Abstract:

Improvements in drilling operations are critical for the development of the petroleum sector. Compromising in any of the drilling constraints will ultimately give rise to some serious wellbore instability issues. In this study, the effect of various cationic biopolymer water-based drilling fluids on the rheology, filtration, shale stabilization and microbial action over shale was investigated. These ions are classified as monovalent cations (K⁺ and Na⁺) and divalent cations (Mg²⁺). According to the rheological results, it was observed that all the three fluids showed pseudo plastic characteristics. Moreover, yield point, gel strength, apparent viscosity and YP/PV ratio for K⁺ drilling mud were far superior than any other salt sample. These parameters clearly represent effective hole-cleaning behavior for potassium ion sample. Likewise, the filtration test for these samples shows that as the size of cations decreases an increase in filtrate volume was observed. As the ionic radius decreases from 1.33 pm for K⁺ to 0.66 for Mg²⁺, loss of filtrate volume increases from 6.4 to 11.2 mL. The larger size potassium ion clogged the pore sizes in the filter paper and substantial reduction in filtrate loss was observed. Furthermore, the cationic solutions when interacted with shale samples obtained from the northern region of Pakistan to investigate the shale swelling and microbial activity. Results revealed three different mechanisms of reactions between the three cations and the shale formation. Microbial activity was witnessed in K⁺ solution after 10 days, which intensified rapidly till Day 30th, thereby completely damaged the shale sample. In Na⁺ sample, water evaporated from the solution, leaving behind the salt crystals deposits on the face of the shale sample. When Mg²⁺ was investigated a surprising result was perceived. The water in the salt solution found it difficult to vaporize, and it remained in the shale sample even after 30 days. On the other hand, K⁺ ion mud was most effective as shale inhibitor. Substantial reduction in shale swelling was perceived in this mud type. These results will be significant for a drilling engineer to avoid any unnecessary problem during drilling operations in the northern Pakistan region.

Keywords: Cation effect; Microbial activity; Shale; Yield point; Consistency index

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-023-02819-y

Chemical Papers 77 (8) 4693–4704 (2023)