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Microseepage

R.W. Klusman Comparison of Surface and Near-Surface Geochemical Methods for Detection of Gas Microseepage from Carbon Dioxide Sequestration. International Journal of Greenhouse Gas Control. 2011. 5,1369-1392. [Pg.113]

The main conclusion of this study is that hydrocarbon-based surface geochemical methods can discriminate between productive and non-productive oil and gas reservoir areas. Variables in surface soils that best distinguish productive and non-productive areas are ethane and n-butane and heavy (C24+) aromatic hydrocarbons. Heavy metals (U, Mo, Cd, Hg, Pb) are possibly indirect indicators of hydrocarbon microseepage, but they are more difficult to link with the reservoirs. [Pg.125]

Both direct and indirect methods were tested in the Lisbon area. Direct methods include the assessment of hydrocarbon compositional signatures in surface soils, outcrop fracture-fill soils and mosses, and 6-ft (2 m) deep free-gas samples. Indirect methods pertain to the major and trace element chemistry of soils to look for alteration effects resulting from hydrocarbon microseepage. [Pg.126]

Free gas samples were collected from 6-foot depth with a GeoProbe drill at 50-meter intervals over Lightning Draw Southeast. The samples were analyzed for C1 to C6 hydrocarbons by GC-FID and fixed gases (He, H2, C02, CO, 02, N2, Ne, and Ar) by GC-TCD. The gas produced from the Leadville Formation is particularly rich in C02 and He, and thus these are key variables for identifying microseepage (Fig. 3). Light alkanes (C2-C6), H2 and C02 are anomalous over the Lightning Draw field, but He is only anomalous off-structure to the southeast and over the water-leg of Lisbon (Fig. 3). [Pg.126]

Saunders, D. F., Burson, K.R.,. Thompson, C.K. 1999. Model for hydrocarbon microseepage and related near-surface alterations AAPG Bulletin, 83, 170-185. [Pg.392]

It appears therefore that the direct detection of hydrocarbon gases is not the only means of identifying areas of active microseepage, but that a myriad of other possible secondary techniques can be used either as adjuncts, or as solitary techniques in themselves, to infer the presence of hydrocarbons in the subsurface environment. Most of these utilise the detection and subsequent analysis of gaseous hydrocarbons, while other methods employ the detection and analysis of liquid hydrocarbons, nonhydrocarbon gases, the presence and relative concentration of bacteria, and even the presence (or absence) of inorganic compounds and elements. For the most part, however, methods that directly measure the hydrocarbon content of soils or soil atmospheres have met with the most acceptance. [Pg.143]

Mass flow is a bulk movement of hydrocarbons in monophase or dissolved in water. It requires an external force (pressure gradient or structural stress) and a well-defined conduit or plumbing system. The microseepage resulting from mass flow is therefore characteristically confined to a small area or belt, within which the anomalies are of high contrast and often contain some high molecular-weight hydrocarbons. [Pg.217]

According to Kartsev et. al. (1959), Sokolov (1970), Horvitz (1986) and Fei and Ruan (1991), gas microseepage associated with petroleum has three characteristic styles of surface anomaly (1) apical (2) aimular and (3) linear. One or any combination of these surface expressions may occur over a given oil or gas field. [Pg.218]

All types of anomalies can be present over a given oil or gas field depending on the relative depth of the field, its caprock lithology and structural control, the gas species in the microseepage, their modes of occurrence, near-surface lithologies and soil types, climate and even the time of year. This wide range of factors renders gas anomaly interpretation difficult. [Pg.218]

The Pinqiao oil field occurs in sandstone lenses of Triassic age, at a depth of less than 1000 m. A gas geochemical survey was carried out over a 1500 km area in order to test for microseepage from the known oil field and detect any neighbouring fields. Soil samples were collected on a 1 x 1 km grid and analysed by the acid treatment method for... [Pg.228]

The surface manifestation of hydrocarbon microseepage in not necessarily confined to the presence of trace quantities of hydrocarbons. Schumacher (1996) made a thorough review of the major hydrocarbon-induced changes affecting soils and sediments and their implications for surface exploration. [Pg.234]

Fig. 7-2. Spectra of minerals associated with hydrocarbon microseepage. Fig. 7-2. Spectra of minerals associated with hydrocarbon microseepage.

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Hydrocarbon microseepage

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