Investigating the effect of matrix acidizing injection pressure on carbonate-rich Marcellus shale core samples: an experimental study

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.

Assessment of oil-producing wells by means of stimulation approach through matrix acidizing: a case study in the Azraq region

“…In this context, the consumed amounts of HCl mixture decrease with interval depth for Hummar formation; this could be attributed to its limestone layer and relatively higher water saturation with respect to Shueib. This finding was inherently confirmed by Khalil et al (2021) in relevant investigations. More focus should be drawn on diverting agent that was needed only in the second acidizing trial for the H2 target well.…”

“…It is vital to extensively consider the damage mechanisms when designing a matrix treatment, such as dissolving calcites, quartz, or clay minerals, which alter the reservoir's behavior toward the acids (Kolin et al and Kurvijc et al 2018). Generally, the hydrochloric (HCl) acid is substantial in enhancing oil production; it is advantageous in eliminating dolomite and limestone materials from reservoirs and is greatly utilized in carbonate acidizing (Chang et al 2008;Khalil et al 2021).…”

“…Besides acids, the inclusion of acidizing additives, such as polymers and corrosion inhibitors, has been shown to significantly affect the mechanism with which the acid reacts to the reservoir's rock. While in the studies of Garrouch and Jennings (2017) and Khalil et al (2021), matrix acidizing with special additives of carbonate reservoirs was performed, through deducing the impact of this stimulation technique on the wells' technical characteristics and the performance of chosen reservoirs before and after acidizing jobs. The wells' technical characteristics include the flow efficiency, productivity indices, and stimulation gain, which have shown a positive response toward acid stimulation.…”

“…According to previous surveys performed by official authorities in this region, the target wells contain superimposed layers of multiple hydrocarbon fractions with considerable estimated amounts, which merit further investments. HCl has significant advantages in acidizing treatment of limestone and dolomite layers, following the studies of Chang et al (2008), Shafiq and Mahmud (2016), Leong andMahmud (2019), andKhalil et al (2021). According to the chemical composition of Shueib and Hummar formation, the corresponding reactions of these structures with HCl acid could be described as follows:…”

Evaluation Approach of Rock Brittleness Index for Fracturing Acidizing Based on Energy Evolution Theory and Damage Constitutive Relation

“…In the aspect of well stimulation for sandstone or carbonate reservoirs, matrix acidizing is regarded as an essential approach. This technique is to inject acid into the formation and then dissolve the matrix [2], which further improves the formation permeability and reduces the breakdown pressure during the fracturing treatment [3][4][5]. Acid corrosion causes the change of the microstructure and mineral compositions, which has weakening effects on the physical and mechanical properties of rocks [3].…”