Sulfur-Bearing Capacity of Hydrogen Sulfide Gas
Authors: Swift S.C. , Manning F.S. , Thompson R.E. 
Published: December 2007

Recent deep drilling bas generated a need for data on the physical and chemical properties of reservoir fluids at high pressures and temperatures. Here, experimental data are presented on the total quantity of sulfur that can be associated with sour gas up to 20,000 psi and 350 degrees F. A model is fitted to the data, thus permitting rational interpolation and extrapolation and prediction of the effect of adding inert materials.

Introduction

Lack of knowledge of the physical and chemical behavior of reservoir fluids at pressures as high as 20,0O0 psia and temperatures up to 400 degrees F is a problem associated with production of deep, problem associated with production of deep, high-pressure reservoirs. Some reservoir compounds, such as CH4 and H20, appear to be quite stable chemically, while others such as H2S and S undergo marked chemical and physical changes.

Experience in attempting to produce deep wells in the Smackover lime of Mississippi indicates that deposition of elemental sulfur in production channels of these wells could completely shut off production. The ability to predict the amount of sulfur deposition to be expected at a given pressure and temperature would be very beneficial. For example, this might permit operation of a particular reservoir so that permit operation of a particular reservoir so that the fluid in that reservoir is produced into the well with no sulfur precipitation in the reservoir rock. Or, this knowledge could be used to design solvent circulation systems within the wellbore to dissolve any sulfur that otherwise might be precipitated.

This study theoretically and experimentally examines the equilibrium behavior of H2S and S at conditions of pressure and temperature up to 20,000 psia and 400 degrees F, respectively. psia and 400 degrees F, respectively. DESCRIPTION OF EQUIPMENT

The heart of the experimental apparatus is the equilibrium cell shown in Fig. 1. This cell is a special design developed with Autoclave Engineers of Erie, Pa. It is constructed of A-286 Amco stainless steel and uses pressure-tightening, metal-to-metal seals on the closures at each end. This provides 12.25 in. of 2-in.-ID volume with a working pressure of 25,500 psia. The cell is fitted with a Monel piston with Viton O-rings that allow a noncorrosive working fluid to apply pressure on the sample across the piston. Constant pressure was maintained on the working fluid with a Murphy switch-gauge that activated a Ruska mercury pump when the pressure fell below a set value. Pressure was measured with a 30,000-psia, 16-in. Heise pressure gauge accurate to + 0.1 percent. Pressure control during equilibration was very good. However, because of piston friction, fluctuations of + 5 percent sometimes occurred momentarily during sampling.

The cell was mounted on a pivot inside an insulated cabinet wad could be agitated externally to accelerate equilibration. The air-bath temperature was regulated by a thermostatically controlled, electrical heating element. The temperature was measured with an iron-constanton thermocouple attached to the outer surface of the equilibrium cell. The cell temperature would drop slightly while taking a sample, but never dropped more than 2 degrees F.

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