Effect of Residual Oil Saturation on the Propagation of Regular, Gelled, and In-Situ Gelled Acids inside Carbonate Formations

Gomaa, Ahmed M.; Nasr‐El‐Din, Hisham A.

doi:10.2118/143643-ms

Cited by 10 publications

(1 citation statement)

References 16 publications

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“…Literature survey shows contrasting results as to how residual oil affects pore volume to breakthrough. Gomaa et al (2011) showed that as flow rate increased, higher pore volumes of regular acid were required to break through cores with residual oil saturation. Shukla et al (2006) claims that residual oil saturations in carbonate cores had little effect on the acidizing process and that these cores have the same wormholing effect as cores completely saturated with water.…”

Section: Effect Of Oil Saturation While Acidizing Carbonate Rocksmentioning

confidence: 99%

Effect of Oil Saturation on Acid Propagation during Matrix Acidization of Carbonate Rocks

Kumar

Nasr‐El‐Din

2014

SPE Latin America and Caribbean Petroleum Engineering Conference

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The existence of an optimum injection rate for wormhole propagation and face dissolution at low injection rates during matrix acidizing are well established. However, little has been documented that describes how the presence of residual oil affects carbonate acidizing. This study demonstrates the impact of oil saturation on wormholing characteristics while acidizing field and outcrop cores under reservoir conditions (200°F). Knowledge of the effect of different saturation conditions on acid performance will contribute towards the design of more effective acid treatments. Coreflood experiments at flow rates ranging from 0.5 to 20 cm3/min were performed to determine the optimum injection rate for wormhole propagation when acidizing homogeneous limestone reservoir cores and low permeability Indiana limestone cores of dimensions 3 and 6 in. length and 1.5 in. diameter. The absolute permeability of the cores ranged from 1 to 78 md. The study involved acidizing cores saturated with water, oil, and waterflood residual oil using 15 wt% HCl. The viscosity of the crude oil used was 3.8 cp at 200°F. CT scans were used to characterize wormholes through the cores. The concentrations of the dissolved calcium and magnesium ions were measured using Inductively Coupled Plasma–Optical Emission Spectroscopy (ICP-OES) and the effluent samples were titrated to determine the concentration of the acid. At injection rates 0.5 to 20 cm3/min, 15 wt% HCl was effective in creating wormholes with minimal branches for cores with residual oil (Sor=0.4–0.5). Compared to brine and oil saturated cores, waterflood residual oil cores took less acid volume to break through. Additionally, the wormholing efficiency of regular acid improved with increased acid injection rates in the presence of residual oil. A decrease in acid pore volumes to breakthrough for oil saturated cores was noted at high acid injection rates, which could be attributed to viscous fingering of acid through oil. Unlike brine saturated and oil saturated cores, waterflood residual oil cores showed no face dissolution at low acid injection rates. Conclusions from this work will aid in the design of better acid jobs by highlighting the impact of oil saturation on wormholing characteristics of acid while acidizing carbonate rocks.

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Section: Effect Of Oil Saturation While Acidizing Carbonate Rocksmentioning

confidence: 99%

Effect of Oil Saturation on Acid Propagation during Matrix Acidization of Carbonate Rocks

Kumar

Nasr‐El‐Din

2014

SPE Latin America and Caribbean Petroleum Engineering Conference

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Assessing the impact of oil saturation on wormhole morphology in carbonate acidizing

Neyra,

Lucas,

Silva

et al. 2024

Fuel

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Wormhole Propagation in Tar During Matrix Acidizing of Carbonate Formation

Al-Mutairi

Al-Obied

Al-Yami

et al. 2012

SPE International Symposium and Exhibition on Formation Damage Control

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Heavy, viscous oil deposits and tar have low °API gravities and occur as part of several oil formations. Unlike normal oil deposits, heavy oil and tar tend to contain more inorganic impurities and to be more sulfurous and aromatic. And as so, they tend to have different responses to acidizing fluids during matrix acidizing treatments. One fundamentally interesting phenomenon is the wormholing characteristics ofacidizing tar formation. This paper discusses the effect of acid and its wormholing characteristic on tar and on carbonate rock that was saturated with crudes that have varying °API gravities. Experiments included acid flooding of core plugs that were saturated with different °API gravities. The extreme case included flooding the acid through tarsaturated plugs. The wormholes were characterized by CT Scanning. Differential pressures, number and sizes of wormholes and breakthrough volumes were all measured for each experiment. The tests involved regular hydrochloric acid and emulsified acids. This study showed that regular and emulsified acids produced comparable wormhole penetration in tar. Tar formations were difficult to exhibit face dissolution even at extremely low injection rates. In general, it was noticed that penetration and, hence, benefit from emulsified acid is reduced when higher °API oil saturated the rock. The wormhole breakthrough volume in a rock saturated with intermediate oil was less than that of a rock saturated with condensate oil. Condensate might have allowed better diffusion of acid droplets to react with the rock. This work provided a fundamental investigation that can lead to development in producing these challenging prospects. In addition, these results are of special interest when long horizontal injectors or producers are placed within the tar zone of conventional oil reservoirs.

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Effect of Residual Oil Saturation on the Propagation of Regular, Gelled, and In-Situ Gelled Acids inside Carbonate Formations

Cited by 10 publications

References 16 publications

Effect of Oil Saturation on Acid Propagation during Matrix Acidization of Carbonate Rocks

Effect of Oil Saturation on Acid Propagation during Matrix Acidization of Carbonate Rocks

Assessing the impact of oil saturation on wormhole morphology in carbonate acidizing

Wormhole Propagation in Tar During Matrix Acidizing of Carbonate Formation

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