Three-dimensional anisotropic swelling model for clay shale —a fabric approach

Canadian International Petroleum Conference

2000

Self Cite

This paper presents a mathematical method for analysis of time-dependent swelling-softening process in clay shale around a drilled hole subjected to fresh water invasion. The model is derived from a set of governing equations involving equilibrium and mass balances for fluid and ions components. Flow laws according to hydraulic, repulsive and osmotic pressure heads are required. Effect of modulus reduction due to swelling must be also taken into consideration. The proposed method was used to simulate the experimental results observed in hollow cylinder tests on Colorado Group shale. Computer tomography scanning method was used to examine the deformation of the hole for a period of 72 days. In addition, the amount of sodium chlorine ions released from the shale specimen into the water was monitored continually. Analysis of the test results show that swelling and softening mechanism is a coupled mechanical-hydraulic-chemical coupled process.

Section: Methods Of Analysismentioning

confidence: 99%

Section: Methods Of Analysismentioning

confidence: 99%

Section: Fluid Flow Continuitymentioning

confidence: 99%

mentioning

confidence: 99%

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Analysis of Swelling and Softening in Shale (Colorado Group) Around a Drilled Hole

Canadian International Petroleum Conference

2000

Self Cite

“…Particularly, under fully drained condition, the thermally induced deformation behavior in clay shale is the combined effect from the thermal expansion of the solid particle and the thermal dehydration of Stern layer in clay particles. The anisotropic deformation behavior can be due to the intrinsic oriented fabric (Cholach and Schmitt 2006; Hornby et al 1994;Wong and Wang 1997). Thermally induced plastic strain happens after the heating processes, and it is due to the sample's irreversible contraction behavior or heat consolidation.…”

Section: Confined Slow Heating Testmentioning

confidence: 99%

Experimental Studies of Thermally Induced Deformation and Fracture Generation in Clay Shale

Diedro

Day 3 Thu, June 12, 2014

et al. 2014

In thermal enhanced oil recovery process, the clay shale formations above the oil sands reservoirs may be subjected to high pressures up to 10MPa and high temperatures up to 300°C. The responses of the clay shale are very critical for designing or operations of thermal recovery processes. Maintaining wellbore and caprock integrities prevents incidents such as borehole collapse and leakage through caprock. Thermally induced deformation and fracturing in shale impacts on wellbore and caprock integrities. Most previous investigations focused on the mechanical properties of the clay shale. However, limited experimental work has been conducted to investigate the thermal response of clay shale under thermal operation conditions.In this research, the thermal response of clay shale under different confining pressure conditions is investigated. Laboratory confined and unconfined tests were conducted on Colorado Shale cores which were retrieved from the overburden shale formation above the oil sands reservoirs in Cold Lake area, Alberta, Canada. The shale cores were heated at different heating rates and were subjected to different pressure conditions. The thermally induced deformation and fracturing responses in shale have been captured by X-ray computed tomography scanning (CT scan). The results show that under slow heating rates the shale sample maintains its integrity but display irreversible contraction after cooling to room temperature. Under high heating rates, the samples lose their integrity.

Quantifying structural states of soft mudrocks

2016

JGR Solid Earth

In this paper, a cm model is proposed to quantify structural states of soft mudrocks, which are dependent on clay fractions and porosities. Physical properties of natural and reconstituted soft mudrock samples are used to derive two parameters in the cm model. With the cm model, a simplified homogenization approach is proposed to estimate geomechanical properties and fabric orientation distributions of soft mudrocks based on the mixture theory. Soft mudrocks are treated as a mixture of nonclay minerals and clay‐water composites. Nonclay minerals have a high stiffness and serve as a structural framework of mudrocks when they have a high volume fraction. Clay‐water composites occupy the void space among nonclay minerals and serve as an in‐fill matrix. With the increase of volume fraction of clay‐water composites, there is a transition in the structural state from the state of framework supported to the state of matrix supported. The decreases in shear strength and pore size as well as increases in compressibility and anisotropy in fabric are quantitatively related to such transition. The new homogenization approach based on the proposed cm model yields better performance evaluation than common effective medium modeling approaches because the interactions among nonclay minerals and clay‐water composites are considered. With wireline logging data, the cm model is applied to quantify the structural states of Colorado shale formations at different depths in the Cold Lake area, Alberta, Canada. Key geomechancial parameters are estimated based on the proposed homogenization approach and the critical intervals with low strength shale formations are identified.