Channel sand

Sayid body finite sand bodies such as channel sands, river delta sands,... 

Almost all of the individual fault blocks, that have been drilled, contain oil and gas. In the western part of Block 30/9 (Omega, B and G structures), the main reservoir unit comprises the predominantly transgressive marine sands in the upper part of the Brent Gp (the Tarbert Fm), whereas channel sands within the Lower and Upper Ness Fms constitute the main reservoir units in the C and J structures. 

Lower Ness sand Fluvial channel Stacked channel sand with high permeability Coarse to medium grained sand... 

The R2A unit of the Lower Ness Fm consists of a sheet of relatively homogeneous and clean channel sands. The thickness variation of the sheet is around... 

The Lower Jurassic succession starts with the terrestrial to marginal marine Are Formation (Hettan-gian-Sinemunian) characterized by medium to coarse channel sands separated by shales and coal layers. 

Figure 13.37 shows the S-ZX pilot test location and locations of other ASP pilot tests and commercial applications in the Daqing oilfield. The target layer, Slli-3, was composed mainly of braided channel sand formed by Lamadian-Saxi fluvial system. Some of the reservoir and flnid data are shown in Table 13.9. 

Dreyer, T., Scheie, A. Walderhaug, O. (1990) Minipermeameter-based study of permeability trends in channel sand bodies. Bull. Am. Petrol. Geol., 74, 359-374. 

Detailed mineralogical and textural analysis of Ugnu Formation has been conducted by Mowatt et al. (1991) and Hallam et al. (1991). The sand bodies with good reservoir parameters in the Lower Ugnu Formation were deposited by the distributary channels of a prograding delta. The coarse channel sands are... 

The presence of coal seams suggests that there were periods of abandonment of delta due to the lowering of sea level. Because the reservoir sands are restricted to channels and their subsequent subaerial exposure and erosion, it is difficult to precisely correlate these sands between wells. In particular, the thickness of these sand bodies changes abruptly and some of the sand layers are absent in some wells. However, the major sand layers are easily identified throughout the field. It should be noted that channel sands observed in one well may not laterally extend Into the adjacent well and may correlate to the sands representing other channels on the delta. These channel sands characteristically contain higher contents of fines near the bottom and become cleaner and coarser near the top. 

The maximum thickness of these channel sands occurs in the Milne Point N-19 and tends to taper towards south and southwest (Figure 9) It appears that these sands were deposited on an east-west oriented delta. The thickness of each sand unit varies considerably as illustrated by the isopach maps in Figures 10 and 11. 

Thus, in summary, note that poor linear, areal and vertical waterflooding efficiency may occur for unfavourable M, and that the role of polymer is basically to remedy this situation by reducing M. However, for linear and areal (homogeneous) sweep improvement it is necessary only to reduce M to approximately unity. In cases where larger scale heterogeneities occur, e.g. vertical stratification or areal channel sands, it may be necessary to reduce M to a value considerably below unity. The desirable M for such cases will depend on the details of the particular system of interest. This may also be constrained by certain practical problems such as the magnitude of additional pressure build-up that is acceptable when using viscous polymers in the field. 

Figure 8.17. Calculated and experimental sweep patterns for a brine flood and a polvmer flood in a heterogeneous channel sand five-spot system (from Slater and Farouq-Ali. 1970a).

Example 15-1. Convergence acceleration, two deviated horizontal gas wells in a channel sand. 

Here,/is initial water cut value before the polymer flood 2 is the proportion of the channel sand body kd is permeability ratio Vk is Dykstra-Parsons coefficient of permeability variation m is well pattern density and 0 is a factor affected by the polymer-injection formula (that is to say, how much the effectiveness is affected by factors such as concentration, viscosity, and polymer-bank size). R is the oil recovery before polymer flood N is the connectivity factor between injectors and producers S is the proportion of wells with separate layers and B is the proportion of the wells that adopted the measures of profile modification. 

Secondary porosity seems to be very widespread in clastic and carbonate sediments and not restricted to particular depth intervals (unpubl. data and Bloch 1991a). For instance, regional porosity/depth data from Miocene channel sands from the Far East (Fig. 1) span the depth range from 4000ft (1219.2m) to 10000ft (3048 m). Secondary porosity ranging up to 14% bulk... 

Fig. 2. Porosity (and density) - depth behaviour of Miocene channel sandstones from a Far East location. Note the predictable decline of porosity with increasing burial depth. Deviations from the regional trend are not in general related to the abundance of secondary porosity. This occurs despite highly variable amounts of secondary porosity present in these channel sands (see Fig. 1). Each symbol type refers to a well...

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