Reservoir souring

A mathematical model for reservoir souring caused by the growth of sulfate-reducing bacteria is available. The model is a one-dimensional numerical transport model based on conservation equations and includes bacterial growth rates and the effect of nutrients, water mixing, transport, and adsorption of H2S in the reservoir formation. The adsorption of H2S by the roek was considered. 

Tables 5-1 to 5-3 summarize some biocides proposed for bacteria control. Core flood experiments were used to evaluate the efficacy of periodic formaldehyde injection for the control of in situ biogenic reservoir souring. Formaldehyde treatments were demonstrated to control souring in both...

N. Macleod, E. Bryan, A. J. Buckley, R. E. Talbot, and M. A. Veale. Control of reservoir souring by a novel biocide. In Proceedings Volume. 50th Annu NACE Int Corrosion Conf (Corrosion 95) (Orlando, FL, 3/26-3/31), 1995. 

K. A. Sandbeck and D. O. Hitzman. Biocompetitive exclusion technology a field system to control reservoir souring and increase production. In US DOE Rep, number CONF-9509173, pages 311-319. 5th US DOE et al Microbial Enhanced Oil Recovery Relat Biotechnol for Solving Environ Probl Int Conf (Dallas, TX, 9/11-9/14), 1995. 

E. Sunde, T. Thorstenson, T. Torsvik, J. E. Vaag, and M. S. Espedal. Field-related mathematical model to predict and reduce reservoir souring. In Proceedings Volume, pages 449-456. SPE Oilfield Chem Int Symp (New Orleans, LA, 3/2-3Z5), 1993. 

D. W. S. Westlake. Microbial ecology of corrosion and reservoir souring. In E. C. Donaldson, editor. Microbial enhancement of oil recovery recent advances Proceedings of the 1990International Conference on Microbial Enhancement of Oil Recovery, volume 31 of Developments in Petroleum Science, pages 257-263. Elsevier Science Ltd, 1991. 

Khatib, Z. I. and Salinitro, J. P., 1997. Reservoir Souring Analysis of Surveys and Experience in Sour Waterfloods. SPE Paper No. 3879 5 SPE Annual Technical Conference and Exhibition, San Antonio, TX, October 5th-8th. 

Larsen, J., 2002. Downhole Nitrate Applications to Control Sulfate Reducing Bacteria Activity and Reservoir Souring. Corrosion/2002, Paper No. 02025, (Denver, CO NACE 2002). 

Some of such problems are reservoir souring and/or filter blockages in diesel systems (communication with Dr. A.M. Qrshed, Production Services Network, Aberdeen, UK, Ol/June/07). 

I. Hutcheon 1998. The potential role of pyrite oxidation in corrosion and reservoir souring. Journal... 

Oil and Gas Production This sector is a major user of corrosion monitoring equipment, in particular for offshore fields where ramifications of corrosion and consequent maintenance are far more serious and costly compared with onshore production. Carbon steel is used for approximately 70-80 70 of production facilities. The development of a field is assessed on a defined corrosion risk which may not be correct, leading to serious corrosion. In addition, a reservoir may become more corrosive as the field is extracted owing to (a) increased water content, and (b) eventual souring of the field (hydrogen sulphide production). 

Among the bacteria that can inhabit an oil reservoir are the sulfur bacteria that use sulfur compounds in their metabolism. These bacteria produce hydrogen sulhde, which has been responsible for extensive corrosion in the oil field. Thus exclusion of these bacteria from MEOR is highly desirable. The net effect of souring a reservoir is a decrease in the economic value of the reservoir [1835]. 

Mueller RF, Nielsen PH (1996) Characterization of thermophilic consortia from tTwo souring oil reservoirs. Appl Environ Mcrobiol 62 3083-3087 Niazi JH, Prasad DT, Karegoudar TB (2001) Initial degradation of dimethylphtha-late by esterases from Bacillus species. FEMS Microbiol Lett 196 201-205 Obst M, Krug A, Luftmann H, Steinbuchel A (2005) Degradation of cyanophycin by Sedimentibacter hongkongensis strain KI and Citrobacter amalonaticus... 

The sour natural gas sulfur recovery industry covers virtually the entire gamut of chemistry. From the sour gas reservoir to the Claus plant end product problems are encountered in thermodynamics, kinetics, corrosion, catalysis, redox, rheology and the environment - plus all the rest In reviewing recent developments in such a wide ranging field it is only possible to select examples. It is hoped, however, that these highlights will serve to illustrate the dynamism of the industry in recent years and the progress it has made in developing a new source of one of the world s most basic and essential elements in an environmentally acceptable manner. 

Although the use of inhibitors can mitigate corrosion to some extent in such hostile environments (15) designing systems with appropriate phase behaviour under bottom hole conditions is difficult. To date oil based inhibitor carrier systems have been employed but these require large volumes of fluid circulation and it is often difficult to maintain a continuous oil wet surface on the tubulars. A water-inhibitor system would overcome many of these problems since the sour gas fluid is already saturated with water in the reservoir. Such a system, however, remains to be designed. 

Ci uuc oil—complex, naturally occurring fluid mixture of petroleum hydrocarbons, yellow to black in color, and also containing small amounts of oxygen, nitrogen, and sulfur derivatives and other impurities. Crude oil was formed by the action of bacteria, heat, and pressure on ancient plant and animal remains, and is usually found in layers of porous rock such as limestone or sandstone, capped by an impervious layer of shale or clay that traps the oil (see reservoir). Crude oil varies in appearance and hydrocarbon composition depending on the locality where it occurs, some crudes being predominately naphthenic, some paraffinic, and others asphaltic. Crude is refined to yield petroleum products. See distillation, hydrocarbon, sour crude, sweet crude, asphalt, naphthene, paraffin. 

There are three important considerations in the selection of an injection zone. They are 1. Containment, 2. Injectivity, and 3. Interactions. A suitable injection zone should also be within a reasonable and economic distance from the compressor location. Large aquifers, depleted reservoirs, and zones that produce sour fluids can be suitable for use as an injection zone. 

World sulfur reserves. The earth s crust contains about 0.6% S, where it occurs as elemental S (brimstone) in deposits associated with gypsum and calcite combined S in metal sulfide ores and mineral sulfates as a contaminant in natural gas and crude oils as pyritic and organic compounds in coal and as organic compounds in tar sands (Tisdale and Nelson, 1966). The elemental form commonly occurs near active or extinct volcanoes, or in association with hot mineral spings. Estimates by Holser and Kaplan (1966) of the terrestrial reservoirs of S suggest that about 50% of crustal S is present in relatively mobile reservoirs such as sea water, evaporites, and sediments. The chief deposits of S in the form of brimstone and pyrites are in Western European countries, particularly in France, Spain, Poland, Japan, Russia, U.S.A., Canada, and Mexico. World production of S in the form of brimstone and pyrites was approximately 41 Tg in 1973 other sources accounted for about 8 Tg, making a total of 49 Tg (Anon, 1973). Byproduct S from sour-gas, fossil fuel combustion, and other sources now accounts for over 50% of S used by western countries, as shown in Fig. 9.1. This percentage may increase as pollution abatement measures increase the removal of SO2 from fossil fuel, particularly in the U.S.A. Atmospheric S, returned to the earth in rainwater, is also a very important source of S for plants. 

As is the case with sorbic acid, benzoic acid penetrates the cell wall in the undissociated form. As a consequence, it is active at lower pH values only (pKa at 25°C = 4.19) and therefore serves as a preservative for sour products such as fruit juices and jams. In shrimp preservation it is applied as a powder that is spread over the shrimps, passes cell walls, and then ionizes in the intracellular fluid to yield protons that acidify the alkaline interior of the cell. The main cause of its activity, however, is biochemical effects (Eklund, 1980) such as inhibition of oxidative phosphorylation and of enzymes from the citric acid cycle (Chipley, 1983). In mayonnaise preserved by benzoic acid, the undissociated acid is mainly present in the lipid phase, which can be considered as a reservoir for the aqueous phase. 

The proposed overall process flow-scheme for the treatment of very sour gases (i.e., with an acid gas content above 20%) with re-injection of the separated acid gases to a disposal reservoir incorporates a special patented H2S pre-extraction step upstream of the Activated M DEA acid gas removal process. In this upstream step [10], called SPREX, a substantial amount of the H2S and some of the CO2 are pre-removed from the wet raw gas as a pumpable liquid stream. This liquid will essentially contain by solubility all the water of saturation that comes with the inlet raw gas. It will also contain some of the incoming hydrocarbons. Figure 10.6 depicts a process flow diagram of this special pre-extraction and Activated MDEA combination process. 

SOUR GAS - A gaseous environment containing hydrogen sulfide and carbon dioxide in hydrocarbon reservoirs. 

A consequence of the use of advanced technology in oil production from a reservoir results in increase in the corrosivity of the oil production environment. The extent of corrosion increases because (i) oil, water, and gas are present in the field. Seawater or fresh water is injected downhole to drive oil out of formation. As time passes, the amount of water to the amount of oil increases and the degree of internal corrosion increases. Water injection from seawater or fresh water sources causes souring of oilfields with H2S and increases in corrosion rate. These water sources require biocide injection and deaeration to avoid the introduction of new corrosion pathways into the existing system. Tertiary recovery techniques involve miscible and immiscible gas floods that may contain as much as 100% CO2. This leads to high corrosivity of the fluids. 

Produced water is usually re-injected into special wells for disposal or to maintain reservoir pressure. Two aspects of water injection corrosion control differ from those involved in producing wells. The first is the need to reduce suspended solids to very low values to avoid plugging the formation at the bottom of the injection well. These solids include steel corrosion products, as well as scales. Sulfide corrosion products are of major concern because of their low solubility. Metal sulfide products can occur because of reactions between metal and the H2S from the sour gas or the H2S generated by sulfate reducing bacteria. 

Nemati, M., Jenneman, G. E. and Voordouw, G., 2001a. Impact of nitrate-mediated microbial control of souring in oil reservoirs on the extent of corrosion. Biotechnology Progress 17, 852-859. 

The seal oil system supplies oil to the hydraulic seals of the compressor, whidi are located at the outer ends of the shaft, at a constant temperature and pressure, nie oil escaping the low-pressure side of the seal returns to the reservoir and is recirculated. Oil escaping through the high-pressure side passes through sour oil traps to the seal oil degassing tank. ... 

There are two types of seal oil systems.- gravity and pressurized. The gravity-feed seal oil system reservoir is mounted above and in view of the compressor, whose elevation is set by the compressor vendor. The sour oil traps can be integral with the lube oil console skid or located on a separate skid. The pressurized seal oil system is a pump-around facility whose components are integral to the lube oil console skid or mounted on a separate d. If components are mounted on a separate skid, placement must accommodate seal oil console operation and maintenance,... 

There are two readily available sources of water Sparky and waterflood water. The waterflood water is a combination of produced water from the Lloydminster zone, produced water from trucked-in McLaren zone wells and make-up water from the Sparky water source zone. The chemical composition of these waters is provided in Table 2. The Lloydminster zone is slightly sour, so for safety concerns, this water source was ruled out and the on-site Sparky water was chosen. The Sparky water made a consistent polymer solution in the field, with good injectivity into the reservoir and low polymer adsorption/retention at the sandface. Polymer has broken through at concentrations of approximately 100 ppm at the nearest producing wells. 

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