Heavy oil recovery processes such as cyclic steam stimula-tion, solution-gas drive and borehole mining involve reducin the in situ effective stresses to a low effective stress close to zero. Understanding how the oil sands behave mechanically at such a low effective stress will provide some insight into geome-chanical impact on each recovery process. This paper focuses on sand production in solution-gas drive. Triaxial compression tests were conducted at effective stresses less than 50 kPa, and the test results were used to analyse the behaviour of a perforation cavity including elastic unloading, yielding and instability. It is found that a perforation cavity retains its integrity even with yielding. Instability or sand production is triggered by seepage force. Hence, the growth of the cavity is controlled by the seei)-age force and its direction. Practical implications regarding eavi-ty growth, inflow enhancement and overburden stability are also addressed. Introduction Cyclic steam stimulation, solution-gas drive and borehole min-ing are the viable in situ recovery methods for oil sands and heavy oil reservoirs in Alberta and Saskatchewan. These three methods involve either elevation of in situ pore pressure or removal of sands, thereby causing a reduction in iii situ effective stresses'.Hence, knowledge of stress-strain relations of oil sands at low effective stresse,,,, is required to investiuate the geomechanical impact on the recovery processes. Iii unconsolidated oil sands, geomechanical behaviour is more iniportant at a low effective stress than at a high effective stress because the stress-strain rela-tions become more non-linear and stress dependent at low stress-es. Most previous ueomechanical tests on oil sands were conduct-ed at high stresses (Agar et al. 1986@ Kosar 1989. Test data at low stresses Lire limited (Plewes, 1986; Won,, et al. 1993). A research prograni has been established at The University of Calgary to investigate experimentally the stress-strain response of oil sands at low effective stresses. Some of the test data will be presented herein and used to analyse its impact t)n heavy oil recovery processes. Because of the space limit. the focus is on sand produc-tion in the solution-gas drive.The solution-gas drive method is eiriergin,, as a viable primary recovery technique in heavy oil and oil sands (e.g., Smith 1988: CIM 1992). Field production data appe,,Ir to suggest that produc-tion mechanisms are rather complex and niay be quite different from those encountered in the conventiotizil solution-gas drive process in structurally rigid reservoirs. One ot' the unique features in this primary production is high production rate associated with 44 0,5 -o@ _ high s@ind pri-)duction. Sand production is believed to increase the effective artnt of inflow near the wellbore. There are at least three possible scenarios for the enhanced permeability zone caused bv sand production: (i) channels, (ii) extensive localized shear band", and (iii) dilatancy over a large volume (CIM 1992). In the past, s...