Strengthening of Carbonate-Based Formation Rocks Natural, Sustainable Materials

Abstract

AbstractGenerating hydraulic fractures with good conductivity is essential for well productivity in unconventional formations. However, hydraulic fractures gradually lose conductivity with hydrocarbon production as fracture surfaces creep closer due to proppant embedment or failure of fracture asperities under increasing effective in-situ stresses and high temperatures. This work proposes adding a widely available, natural-based metal carbonate (MC) to fracturing treatments in carbonate formations to make fractures mechanically harder and enhance long-term well productivity. An MC-based formula of varying concentrations was prepared and tested on homogenous carbonate core samples. Two solutions were formulated by mixing 10 and 20 gm of MC powder in 100 ml of organic solvent. The core samples were immersed in different solutions for seven days, and the samples were thoroughly characterized before and after exposure to the solutions. Rebound hammer tests were also conducted to show the effect of the solutions on the samples’ mechanical properties, such as Young's modulus and compressive strength. The test results show that the physical properties such as dry weight, bulk density, and bulk volume of all core samples increased noticeably after treatment, reflecting the success of the precipitation reaction and the penetration of used MC into the bulk of the rock samples. Rock treatment with the 10-20 gm-powder solution led to a significant enhancement of the samples’ mechanical properties, where Young's modulus (E) and Unconfined Compressive Strength (UCS) were observed to increase by up to 34% compared to untreated rock samples. Rock hardening in fracturing applications is a relatively new concept. Compared to the consolidation additives in the literature, the proposed MC formula is ubiquitous, widely available, and inexpensive. Lastly, the MC formula is also a by-product of a few oilfield operations, making it a sustainable solution to industrial waste in the oil industry.