Sand Production in Oil Sand Under Heavy Oil Foamy Flow
Authors: Wong R.C.K. 
Published: March 2010

Sand production and foamy oil flow are the two key factors contributing to successes in cold flow production in Alberta and Saskatchewan. However, the two mechanisms have been studied and treated separately as geomechanics and multiphase flow problems, respectively. This paper describes special experiments that were designed to combine these two processes, and conducted to study their interaction. The experiments involved flow of heavy oil with no dissolved gas (dead oil) and heavy oil with dissolved gas (live oil) in natural, intact heavy oil sand cores. It was found that gas nucleation in heavy oil is the major factor in causing the initiation of sand production in oil sand. This finding is consistent with field observations. A mathematical framework for sand production in heavy oil reservoirs was developed based on the experiments' observations. This model includes the effects of geomechanics and gas exsolution phenomena such as strength of oil sand, stress distribution in the reservoir, solution gas diffusion, foamy oil gas, and fluid phase properties.

Introduction

Sand production and foamy oil flow are interrelated mechanisms in primary production (cold production) of heavy oil reservoirs in Alberta and Saskatchewan. Massive sand production could cause excessive deformation in oil sands and the overburden, resulting in detrimental effects on the wells and production facilities. However, sand control measures tend to reduce the oil production rate. Numerical studies(1–4) have been conducted to predict sand production in heavy oil reservoirs. However, limited experimental work has been performed to study the sand production in oil sand. Tremblay et al.(5, 6) used a computer tomography imaging technique to examine the sand production process in sandpack columns using dead oil injected at a constant rate. They observed that a channel-like cavity was developed and evolved under a critical flow pressure gradient. However, there is no reported experimental study on sand production using natural oil sand cores and live heavy oil. The main objective of this paper is to investigate the effects of bitumen, oil sand interlocked structure, pressure gradient, and gas exsolution on the sand production near a perforation in a heavy oil reservoir. The first part of this paper describes the testing material, testing equipment, test details and results. The second part focuses on the interpretation and analysis of the test results and field observations, followed by conclusions. Details of the mathematical models used in the analysis of the test results are presented in the Appendix.

Testing Material and Equipment

The oil sand cores (Clearwater formation) for the experimental study presented in this paper were recovered at a depth of 424 m from an observation well (3-66-4-W4M) at a site near Cold Lake, Alberta. Core sampling was carried out using a conventional rotary core barrel of 89 mm inside diameter. Cores recovered were frozen at the site and kept inside PVC tubes in a freezer. Prior to any testing, the frozen cores were X-Rayed for sample selection.

A high-pressure (70 MPa capability) stainless steel triaxial cell was used to conduct the sand production tests.