Hydrocarbon-water contact

Hydrocarbon-water contact movement in the reservoir may be determined from the open hole logs of new wells drilled after the beginning of production, or from a thermal decay time (TDT) log run in an existing cased production well. The TDT is able to differentiate between hydrocarbons and saline water by measuring the thermal decay time of neutrons pulsed into the formation from a source in the tool. By running the TDT tool in the same well at intervals of say one or two years (time lapse TDTs), the rate of movement of the hydrocarbon-water contact can be tracked. This is useful in determining the displacement in the reservoir, as well as the encroachment of an aquifer. 

Give the probable hydrocarbon/water contact. Give the probable nature of the hydrocarbons and the gas/oil contact. 

Hydrocarbon/water contact at 9750 ft with curve. Oil to 9696 ft. Gas above with neutron density. 

Looking at the curve, where is the hydrocarbon/water contact ... 

Is there a hydrocarbon/water contact Where Which curve(s) will tell us ... 

That surfactant molecules form aggregates designed to remove unfavourable hydrocarbon-water contact is not surprising but the question that should be asked is why the aggregates form sharply at a concentration characteristic of the surfactant (the cmc). From the basic equation of ideal solution thermodynamics... 

The reason for the success of such a simple model is that the dominating force in determining the surfactant composition on the surface originates from the free energy gain of replacing hydrocarbon-water contacts with hydrocarbon-hydrocarbon and water-water contacts when a surfactant molecule is adsorbed into the surfactant monolayer. 

The effectiveness of the method is most probably based on the fact that alkyl hypochlorite is formed at the oil/water interface where the cosurfactant alcohol resides. The oxidation that follows takes place either inside or on the surface of oil droplet. The rate of the reaction can result from a large hydrocarbon/water contact area permitting interaction between oil-soluble sulfide with interfacial cosurfactant that served as an intermediary. An extension ofthis procedure to mustard deactivation has also been proposed [20b]. Such systems could be also applied to the degradation of several environmentally contaminating materials The formation of microemulsions, micelles and vesicles is promoted by unfavourable interactions at the end sections of simple bilayer membranes. There is no simple theory of solute-solvent interactions. However, the formation of... 

Various terms that are generally used to describe a trap are given in Figxire 5.1. A trap may contain oil, gas or both. Where separate oil and gas phases occur together in the same trap, the gas overlies the oil because it is less dense. The oil-water or gas-water contact is the level below which all pores are completely filled with water. The hydrocarbon-water contact is an equipotential surface. 

Figure 5.9 Relation between the angle of tilt (tan a) of the hydrocarbon-water contact and the horizontal hydraulic gradient Ahy/Ax (after Hubbert, 1953. Reprinted by permission of the American Association of Petroleum Geologists).

Those that occur in conventionally closed lithological structures (i.e. in hydrostatic traps). In these traps the hydrocarbon-water contact may have any degree of tilt from the horizontal to the maximum dip of the barrier boundary at the downstream side of the closure. Although hydrocarbons may become trapped in the conventional hydrostatic traps of sufficient sealing capacity, the hydrocarbon accumulation is not necessarily present in the same position within the trap, as its actual position depends on the hydrodynamic condition in the carrier-reservoir rock (Figure 5.10). 

Finally, there is still a trapping configuration which, although quite common, is often overlooked or misunderstood, the so-called perched water-contact (Johnson et al., 1986 Weber, 1995). This occurs when a reservoir has a U-tube shape with a fault seal or a pinch-out at the closed end. The water cannot escape from this side of the U-tube resulting in different hydrocarbon-water contacts in the same reservoir. In the North Sea, we find perched oil-water contacts in Fulmar (Fig. 16), Tern, Ulla and Logger fields, but there are probably many more cases. 

Weber, K.J. 1995. Perched hydrocarbon-water contacts - a common but poorly understood phenomenon. In Extended Abstracts, Vol. 2, F035, 7th EAPG Conf. and Tech. Exhib., Glasgow, UK. EAPG Business Office, Zeist, pp. 1-2. 

The generation of communication and drainage maps for potential compartments and the correlation and integration of these with hydrocarbon/water contacts, pressure test and production data. 

The well successfully tested gas-condensate with a GOR of 11 000 scf/bbl, the highest in the field, and encountered a hydrocarbon-water contact at 12440 ft (tvdss), some 682 ft below that in the 30/7a-llz well. 

For the 30/7a-P16 fault compartment, an initial sub-vertical well was drilled to define the hydrocarbon-water contact, predicted to occur between 11 444 and 11 758 ft (tvdss). This would then be sidetracked with a sub-horizontal well, about 100 ft above the contact. The pilot hole encountered an undepleted accumulation with a contact close to 11444 ft (tvdss) and showed the crestal part of the structure had a common contact, but that the bounding faults between the compartments were sealing, at least initially, on a production timescale. 

The driving force of micelle formation is the elimination of the contact between the alkyl chains and water. The larger a spherical micelle, the more efficient this is since the volume-to-area ratio increases. Decreasing the micelle size always leads to an increased hydrocarbon-water contact. However, if the spherical micelle was made so large that no surfactant molecule could reach from the micelle surface to the centre, one would either have to create a void or some surfactant molecules would lose contact with the surface. Both of these options are unfavourable. 

FIG. 1 The ratio between the radius of the surface of the tension ifs.o.t. and the radius of the hydrocarbon-water contact surface R for a Winsor II water-in-oil microemulsion droplet. The calculation is based on the general equation [Eq. (160)], and assumes the following curvature-dependent interfacial tension y = 1.00x10 -1.28 x 10 ... 

In forming a micelle, amphiphile chains aggregate in the micelle s core to reduce expensive hydrocarbon-water contact. It is possible to imagine that the chains could pack in a frozen array of parallel dXL-trans chains, and indeed this is the packing found in solid bulk R-alkane. However, without considerable expensive hydrocarbon-water contact, it is impossible to see how such an array could exist in a globular micelle. We should expect, therefore, that the interior of a micelle is liquid, and that the alkyl chains are conforma-tionally disordered. This expectation is borne out by experiments, among the most definitive of which are... 

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