Hydrocyclone Field Tests for Removal of Sand From Production Wells in South Oman
Authors: Hagemeijer P.M. , Jagernath S. 
Published: March 2010

Petroleum Development Oman is developing a major oil field, Haima West, to increase production levels using a new production technology not previously applied in Oman. The wells will co-produce large quantities of sand to improve productivity. The sand needs to be separated from the well fluids at the surface to protect the integrity of the production facility. No sand separation technology has been tested elsewhere in operating conditions comparable to Haima West.

This paper describes the results of field tests performed on a hydrocyclone, processing the high viscosity multiphase fluid. The objectives of the tests were to evaluate the sand separation performance and determine the capacity for the Haima West conditions.

In total, 100 tests were conducted and the main findings were:At very low GLR (&lt; 5 Std.m3/m3) the differential pressure should be at least 200 kPa to obtain recoveries of over 80% at a feed particle size of 200 micron (d80 = 200 micron).The recovery was improved in a step change when free water, in excess of 20% of the crude flow, was added.Gas reduces the gross handling capacity for a given pressure differential over the hydrocyclone.Gas, particularly at low differential pressures (&lt; 200 kPa), has a beneficial effect on the separation performance.

To the authors' knowledge, this is the first time that such complex tests have been undertaken in the field. The impact of gas and free water on the separation performance have not previously been observed and documented.

Introduction

Petroleum Development Oman has recently started the redevelopment of a major oil producing reservoir, "Haima West," in South Oman(1). This development utilizes horizontal wells, with artificial lift, in which co-production of sand is a key element. The chosen well completion, without application of downhole sand control, is new in Oman but Canada's heavy oil industry(2) has benefited from co-production of sand. Initial production rates (per unit well length) for Haima West wells without sand control were demonstrated to be three times more, compared to wells with sand control(1). The economics of this development are extremely attractive.

Production of large quantities of sand has a definite impact on the integrity of the sub surface and surface facilities. Loss of integrity can manifest itself as a safety or environmental risk as well as causing production deferments. The effects of sand production on a facility's integrity as well as the application of surface sand removal equipment are relatively new areas in the oil and gas industry.

This article reviews the application of hydrocyclones for sand removal in Haima West. In particular, it reports the results of field tests to determine the relationships of the separation efficiency and hydrocyclone capacity to various operating parameters.

Review of Previous Work

Hydrocyclones have been operated in the field for many years; References (3) to (6) provide a comprehensive and qualitative overview of the application of this technology. In the following, a synopsis of this previous work is discussed in relation to the Haima West conditions.