Estimates of Stress Dependent Properties in Tight Reservoirs: Their Use with Drill Cuttings Data

Abstract

Abstract The objective of this paper is to present a methodology using drill cuttings for making estimates of porosity, permeability and compressibility as a function of confining pressures in tight formations. An easy to use correlation is developed by comparing results from experimental work including hysteresis at various combinations of overburden and pore pressures in vertical and horizontal core plugs, and permeabilities and porosities determined in the laboratory from drill cuttings. The work is important because of the presence of stress-dependent slot and/or microfracture porosities and permeabilities in tight formations that can affect significantly reservoir performance and forecasting. Recent work has shown that drill cuttings can be used quantitatively for complete petrophysical evaluation (for example determination of porosity, water saturation, pore throat aperture, Young Modulus, Poisson's ratio and brittleness index (Olusola and Aguilera, 2013; Ortega and Aguilera, 2014). The methods have been shown to be useful in those instances where cores and specialized well logs are scarce. Those methodologies are extended in this paper to quantitative evaluation of stress dependent properties. It is concluded that drill cuttings are important direct sources of information that can be used for developing estimates of stress-dependent properties particularly in those cases where cores and specialized logs are scarce or not available. The methodology and correlation are presented in detail as well as a practical application. Although the main and novel contribution is the development of an easy to use correlation for stress-dependent tight reservoirs using drill cuttings, the correlation can obviously be used if only plug data are available.