A Novel Coreless Injectivity Technique for Evaluating Formation Damage in Argillaceous Reservoirs

Abstract

For waterflooding in argillaceous reservoirs, the injection water needs to be carefully designed to avoid formation damage by clay swelling and migration. Common methods of achieving this are compatibility tests of injection water with formation water and rocks and injectivity tests. However, such tests are often not practical nor even possible due to the limited availability and prohibitive cost of obtaining actual reservoir cores. The objective of this work was to develop a cost-effective method to evaluate injectivity that does not require the use of reservoir core. In this study, a novel coreless injectivity method was developed and validated. The method utilizes field-produced drill cuttings to make synthetic core plugs, which are universally available during well drilling and commonly considered as waste. A specially designed cleaning process was performed for the drill cuttings. They were then wet compressed with a high-pressure hydraulic press and dried in a constant-humidity oven to make core plugs with standard dimensions. Drill cutting plugs prepared in this way can then be used for injectivity tests as an alternative to actual reservoir core plugs. The routine core analysis revealed that, although sedimentary structures were lost, the drill cutting plugs preserved the mineralogy and maintained comparable porosity and permeability to the reservoir plugs. To validate the representativeness of the formation damage tendencies of the drill cutting plugs, water injectivity tests were carried out on both preserved reservoir cores and compressed drill cutting cores, using simulated injection water with successively lower salinities. The results showed that injectivity loss as indicated by increasing pressure drop was consistent with both types of cores. The "coreless injectivity evaluation" technique can be applied for argillaceous reservoirs with formation damage concerns. It is a cost-effective and viable technique for evaluating water injectivity when reservoir cores are unavailable.

Preliminary analyses of synthetic carbonate plugs: consolidation, petrophysical and wettability properties

“…In addition to the information reported by Florez et al (2019), some recent works were found from 2017 to 2019, aiming at the same approach (Fedrizzi et al, 2018;Luo et al 2018;Wang et al 2017). Wang et al (2017), during the construction process, embedded NaCl grains (1.45, 1.66, 2.9 and 5.8 g) of average particle size of 3 mm and aluminum (18,27,36 and 45 foils) with radius of 1.5 mm and a thickness of 20 lm into a blend of mass ratio 50:1 composed of carbonate drilling cuttings with average grain size of 120 lm and epoxy resin (epoxy type GCC135 and curing agent W93).…”

“…Despite the points of similarity that the authors show of the constructed samples with the carbonate rocks (chemical and petrophysical), the construction of representative synthetic carbonate plugs also requires the characterization of rock-fluid interaction. Luo et al (2018) cleaned drill cuttings using a solution of 3% w/w KCl under high agitation and then dried them in an oven at a constant temperature of 60°C and 45% humidity. Then, they were placed into a cylindrical pipe with toluene, and pressure of 5000 psi was applied for 30 min to consolidate the synthetic plugs.…”

Construction and evaluation of synthetic carbonate plugs.

“…CHILINGAR; BEESON, 1965;FEDRIZZI et al, 2018;WANG et al 2017;LUO et al 2018 that increasing the quantity of NaCl grains the permeability increases with the increase of total porosity, contrary to the observed with aluminum foils which decrease the permeability and increase the porosity, increasing the quantity of aluminum foil used.…”

“…Therefore, using the same base material, Luo et al (2018) prepared drill cuttings with toluene as a packing fluid and then, they applied a compression press of 5000 psi for 30 minutes to consolidate the synthetic plugs. As the main objective of this research was the evaluation of formation damage using synthetic plugs, the influence of compression press and drill cuttings particle properties in the petrophysical properties was not identified.…”