Production Testing from Cuttings
Evensen, Joseph M.
Age and storage condition of drill cuttings (e.g., hot West Texas warehouses) seem to markedly affect quality of their residual pore fluid contents. Recent PVT investigations, however, have observed inhibition of pore fluids to evaporate beyond certain thresholds in cuttings. Presumably such kinetic effects stem from pore- and mineralogical surface-related fluid-rock properties (i.e., wetting effects, meniscus behavior). Yet acknowledgment of fluid remnants in cuttings is helpful because it permits lab workflows that may (using proper loss correction factors) successfully link responses of cuttings back to their reservoirs.
Standard correction factors for magnitude of loss ("L Factors") have been calibrated for siliciclastic and carbonate cuttings according to time and environmental conditions. By identifying threshold contents of fluids-in-cuttings (gases, liquids, condensates), a growing database for L Factors gives rise to reservoir fluid sampling from fresh or stored cuttings.
Production testing of rock chips has been established by an experimental petrology method that takes advantage of fundamental PVT relations. Micro-production test profiles ("microPT") may be routinely acquired. Recovery data are generated when cuttings are subjected to multi-stage and multi-variable "production", simulated physically in the lab ("Syn-P"). Test runs often include responses to a combination of PVT environment, time, drawdown, build-up, and fragmentation. Patterns resulting from Syn-P show fluid yield character from cuttings sourced by reservoirs, non-reservoirs, or outcrops.
Testing over time establishes a basic production profile, wherein initial production behavior is strongly evident. Build-up and drawdown testing offer early data support for maximization of well production (design). Tests focused on fragmentation - a guiding proxy to fracking/completions - reveal the limits that effective surface area exerts on the efficiency of fluid yields. Because test procedures utilize reservoir material itself, results are genetically scalable between reservoir and stock tank conditions. Test-based petrophysical log data obtained in this manner ("microPLT") can be used to profile well performance prior to well startup.
By making the most of the residual fluid contents within cuttings, microPT data independently establish or improve predictions of reservoir performance.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013