Video: Observations and Complexities in Experimental Measurement of Acid Fracture Conductivity for a Deep Carbonate Field in Kazakhstan
- D. McDuff (Chevron Energy Technology Company) | S. Malhotra (Chevron Energy Technology Company) | B. A. Comeaux (Chevron Energy Technology Company) | B. W. Quintero (Schlumberger)
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- Society of Petroleum Engineers
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- 2018. Copyright is retained by the author. This presentation is distributed by SPE with the permission of the author. Contact the author for permission to use material from this video.
- 5.8 Unconventional and Complex Reservoirs, 2 Well completion, 5.5 Reservoir Simulation, 5.8.7 Carbonate Reservoir, 4.1 Processing Systems and Design, 5 Reservoir Desciption & Dynamics, 4.1.2 Separation and Treating, 4.3.4 Scale, 4 Facilities Design, Construction and Operation, 1.6 Drilling Operations, 2.6 Acidizing, 5.5.3 Scaling Methods
- Experiment, Acid fracture conductivity, Acid fracture, Lab testing, Kazakhstan
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Acid fracture conductivity experiments provide information valuable to effective design of acid fracture stimulation treatments in carbonates. They are complex tests, and a number of procedural details must be taken into consideration in order to upscale results to an adequate representation of well-scale acid fracture behavior for well productivity predictions. This paper focuses on a study performed on analog, quarried limestone core samples and a small number of reservoir core samples from the Unit 2 formation of Kazakhstan's Tengiz field to understand the impact of different acid fluid systems and procedural steps on acid fracture conductivity.
The physical structure of the etched channels is observed to be impacted by the nature of the fluid and has a strong impact on the conductivity. The quality and uniformity amongst the core samples has a critical impact on the measurements and is assessed. The residence time of the acid in the acid-etched experimental channel is small, and the equivalency of acid volumes injected at the experimental scale to the large acid volumes injected into a well-scale fracture channel is considered. Special consideration is given to the procedure of applying stress to and measuring conductivity of the experimental acid fracture channel which may result in large-scale mechanical failures of the core sample, preventing a high-quality measurement of conductivity following injection of a closed fracture acidizing stage.
This body of work discusses the design options and challenges which play a role in defining the testing strategy for an acid fracture conductivity study. Results demonstrate that with selection of appropriate fluid systems, acid fracture conductivity can be retained up to a closure stress of 6,000-7,000 psi in the Tengiz Unit 2 reservoir. A modified stress ramp-up procedure to improve closed fracture acidizing conductivity testing results obtained through the testing program is presented.