Solids Problem At the Ring Border Gas Plant
Authors: Catalan L.J.J. , Jamaluddin A.K.M. , Stepanic D.W. , McNichol P.A. 
Published: March 2010

Natural gas production from the Ring Border Montney formation presents unique problems related to solids deposition during processing since the produced fluids (gas and condensate) contain suspended and dissolved solids. Solids deposition occurs not only in the plant inlet separators but also in the various gasstream and condensate-stream operating units. To address the solids problem at the plant, a large number of deposited solids and condensate samples from several operating units were collected and characterized.

Results of the characterization studies indicated that all types of samples contain various amounts of asphaltenes, wax, insoluble organic carbon, and formation fines. Precipitated asphaltenes were identified as the major contributor to the solids problem. Commingling of two compositionally incompatible condensate streams (one from the low temperature separator and the other from the inlet separators) was found to significantly augment solids deposition in the plant by precipitating out asphaltenes which were initially dissolved in the condensate. Asphaltene precipitation experiments carried out in the laboratory confirmed the compositional incompatibility of the two condensate streams.

Various possible remedial strategies such as chemical injection and process modifications have been evaluated by means of laboratory testing and process simulation. It was found that chemical injection is not effective for preventing asphaltene precipitation at economical chemical injection rates. The process modifications which are recommended to solve the solids problem in the condensate processing units involve separate stabilization of the two incompatible condensate streams and removal of the precipitated asphaltenes downstream of the process using a sedimentation tank.

Introduction

Canadian Hunter produces about 2,400 E3 m3/day of natural gas and about 120 m3/day of condensate from the Ring Border area. The production comes from six zones in the Montney formation at depths ranging from 900 to 1,000 m. The upper, middle, and lower zones may contain any combination of dry gas, gas condensate and/or oil. All wells produce mixed fluids with an asphaltene content that can reach 6% by weight. Production from eighty six wells is collected at nine satellites which are linked by major gas and liquid pipelines to the Ring Border gas plant. The plant is designed for 2,400 E3 m3/day of sales gas using a propane refrigeration process to treat the gas to meet the hydrocarbon dewpoint specifications. The sales gas is then shipped into Alberta via the Nova pipeline system. The condensate is stabilized and stored in an 800 m3 storage tank prior to shipment via a 4 in. liquids pipeline to the Amoco Chinchaga plant for handling and eventual shipment to Edmonton, Alberta. The existing process facilities are illustrated in Figure 1.

Solid problems have been experienced in the plant since startup in 1991. These problems have occasionally resulted in the delivery of condensate to the Amoco Chinchaga liquids facility that exceeded the BS&W (basic sediment and water) specification of 0.5% by volume, resulting in the necessity to divert the condensate to alternate facilities for further processing. Also on several occasions during 1994, it was necessary to manually remove an excessive solid build-up in the stabilizer feed tank.