An Alternative Method of Dealing With Pressure: Friction Reducer for Water Packing of Long Horizontal Open Holes in Low-Fracturing-Gradient Environments

Abstract

Abstract Water packing is the most commonly used gravel packing technique for openhole horizontal completions. With this technique, the packing of a horizontal well occurs through two sequential events, called the a-wave and the ß-wave. Because the carrier fluid is diverted into and must travel through the narrow annulus between the screen base-pipe and the wash-pipe all the way to the toe, pressure builds up steadily during the ß-wave as the packing proceeds from toe to heel, due to high friction pressures in that annulus. This rise in pressure may result in exceeding the fracturing pressure of the reservoir, which in turn causes a premature screenout and an incomplete gravel pack. This is a well known problem, which in the past often limited the horizontal well length that can be gravel packed in many deepwater developments, due to narrow operating window. Today, various solutions are available to solve this problem, including mechanical solutions that create a short cut for fluid returns, and the use of light weight gravel which allows pumping at lower rates without having to worry about gravel settling in the work string but still have a a-wave height that will cover the screens. In this paper, we present an alternative method of dealing with the pressure rise during the ß-wave, reducing the friction pressures through addition of a friction reducer to brine carrier fluid. We first detail the laboratory scale experiments used for screening of many additives considered, including laboratory scale friction pressure measurements, compatibility with high density brines, gravel settling, formation and gravel pack damage. We then discuss the results from full scale friction tests conducted in pipe and annular geometries, using the best candidate friction reducer selected based on laboratory tests. The results indicate that a drag reduction of 40 to 50% is attained with an environmentally friendly friction reducer, with retained permeability of about 90%, and with minimal to no impact on gravel settling and thus a-wave height. Introduction Openhole gravel packing is often the preferred sand control technique in deepwater reservoirs that are prone to sand production. Water packing is one of the two common techniques to gravel pack openhole completions. This technique relies on high local velocities for gravel transport as it uses a low viscosity fluid as the suspension medium. The alternative to water packing is the use of a viscous fluid for gravel suspension, typically in conjunction with alternate path screens.1 Both techniques have their justification based on the individual well and reservoir characteristics and have been successfully deployed in various completions. This paper will focus on one of the major risk factors involved in water packing: exceeding fracturing pressure. A simplified technique is introduced to widen the operational window and minimize the risk of exceeding fracturing pressure.