CHOPS Without Sand
Authors: Wagg B.T. , Fang Y. , Birkett D. 
Published: March 2010

Heavy oil producers in Canada have adopted the primary production strategy of encouraging sand production in a process commonly know as Cold Heavy Oil Production with Sand (CHOPS). While this technique yields economic oil rates, the production of sand introduces many other operating costs and prevents the implementation of technologies, such as gathering lines, that are not compatible with massive sand production. A new concept has been proposed that takes advantage of the reservoir processes of CHOPS but removes most of the extra operating costs and barriers to technology associated with sand production. This paper discusses the new process, how it could benefit heavy oil production operations and the technical challenges that need to be addressed before this concept can be implemented.

Introduction

The Alberta Energy and Utilities Board reports that Alberta has approximately 260 million cubic metres of remaining established reserves of heavy oil that are accessible by primary production(1). Cold heavy oil production with sand (CHOPS) is currently one of the key production techniques being used to develop these reserves. Heavy oil producers in Western Canada have generally accepted the notion that non-thermal heavy oil production is not economically feasible without allowing, and often promoting, sand production. This operating strategy led to operators producing as much as 500,000 m3 of sand per year(2). Handling and disposal costs for this by-product of oil production normally exceeds C$100/m3. In addition, workovers on producing wells due to sand accumulation in the wellbore and downhole pumps and increased wear due to the presence of sand in the produced fluids routinely accounts for over 25% of heavy oil operating costs (based on information provided by Pengrowth Corporation).

Produced sand generally requires special handling facilities, separation equipment and some method of ultimate disposal. Many operators currently dispose of the produced sand in salt caverns. Some of these caverns were initially used for liquid and gaseous hydrocarbon storage, while more recently, some operators and service companies have constructed caverns expressly for produced sand disposal. The current production technique of CHOPS, however, requires the sand to be pumped to the surface, separated in surface tanks, trucked to a central facility, stockpiled and finally injected into the salt cavern. This process is expensive and increases the risks related to safety and environmental mishaps due to increased handling and transportation of sand over potentially long distances and prolonged surface storage.

The present method of producing heavy oil uses lease storage tanks for collecting produced fluids from either single or small groups of wells. In most cases, these lease tanks are open to the atmosphere. While significant quantities of solution gas, principally methane, are produced, this gas is generally allowed to vent to the atmosphere. Measurements of the gas vented from heavy oil wells in Western Canada by New Paradigm Engineering(4) indicate that the volume of gas produced is likely on the order of 700 m3/day per well. Reducing this volume of vented 'greenhouse gas' has become one of the more prominent mandates of the oil industry and governments as a whole.