Investigating the effect of matrix acidizing injection pressure on carbonate-rich Marcellus shale core samples: an exper
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Investigating the effect of matrix acidizing injection pressure on carbonate‑rich Marcellus shale core samples: an experimental study Rayan Khalil1 · Hossein Emadi2 · Faisal Altawati2 Received: 12 July 2020 / Accepted: 13 November 2020 © The Author(s) 2020
Abstract Near-wellbore damage, which significantly reduces hydrocarbon production, can happen during drilling, cementing, perforation, completion, and stimulation operations. The most common technique to remove or bypass this damage is matrix acidizing. The effects of matrix acidizing injection pressure on acid penetration rate, chemical reaction rate, solubility, porosity, and permeability of Marcellus core samples were investigated in this experimental study. To achieve a successful acid treatment, acid type and concentration must be carefully selected. The results of the X-ray powder diffraction (XRD) and the solubility test revealed that 15 wt.% hydrochloric acid (HCl) is the optimum acid. Matrix acidizing treatments were implemented on nine core samples, taken from Marcellus (shale gas reservoir), at the reservoir temperature (66 °C), confining pressure of 10.35 MPa, and three different acid injection pressures (1.72, 3.45, and 5.17 MPa). The results showed that performing acid treatments on the samples containing continuous carbonate layers created highly permeable channels (wormholes) resulting in significant improvement, up to 3900%, in the permeability of the samples. Additionally, the results of the acid penetration rate, chemical reaction rate, solubility, porosity, and permeability revealed that increasing the acid injection pressure resulted in increases in the aforementioned properties of the samples. The results also revealed that any increase in the injection pressure above 3.45 MPa did not demonstrate any significant enhancements in the properties of the samples. The results of the XRD analysis revealed that matrix-acidizing treatments dissolved 23.2% of calcite and 0.4% of dolomite existed in the samples. Keywords Unconventional resources · Matrix acidizing · Effective porosity · Permeability enhancement
Introduction According to EIA (2015), the US oil and gas production from unconventional reservoirs, which have ultimate-low permeability (microdarcies to nanodarcies), has been tremendously improved since 2007. Even though horizontal drilling and multistage-hydraulic fracturing are necessary to produce with economical rates from such reservoirs (King 2011; Mohanty et al. 2019; Warpinski et al. 2009; Zoback and Kohli 2019), the oil and gas production rates significantly decrease by 90% in the first two to three years of * Rayan Khalil [email protected] 1
Faculty of Earth Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
Texas Tech University, Lubbock, USA
2
production (Zoback and Kohli 2019). Despite implementing horizontal drilling and multi-stage hydraulic fracturing, unconventional oil and gas recovery factors are still ultimatelow, 10% in oil reservoirs and 25% in gas reservoir
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