Changes

In this stage, it is necessary for the geologist to subdivide each well (reservoir quality profile) into relatively homogeneous units or zones. Initially it is best to construct a relatively detailed zonation reflecting major variations in reservoir rock characteristics regardless of their vertical dimensions (Figure 4).

In this stage, it is necessary for the geologist to subdivide each well (reservoir quality profile) into relatively homogeneous units or zones. Initially it is best to construct a relatively detailed zonation reflecting major variations in reservoir rock characteristics regardless of their vertical dimensions (Figure 4).

Zonation may be facilitated by establishing criteria by which major categories of reservoir rock types present can be distinguished. Semilog crossplots of porosity and permeability keyed to texture, matrix content, and diagenetic component content are very useful. Through examination of these plots, the geologist can quickly separate samples into natural groupings (Figure 3). Because permeability directly reflects fluid flow capacity, it is the major parameter used to designate reservoir rock categories. Because porosity is commonly a major control on permeability, it generally exhibits a positive correlation with that variable. Attempts to create hierarchies of permeability heterogeneity based strictly on depositional criteria (Lewis, 1988) should be avoided in reservoirs where diagenetic alterations are major controls on permeability heterogeneity. If natural groupings are not present, it may be necessary to set arbitrary group boundaries, such as porosity or permeability cutoffs.

Zonation may be facilitated by establishing criteria by which major categories of reservoir rock types present can be distinguished. Semilog crossplots of porosity and permeability keyed to texture, matrix content, and diagenetic component content are very useful. Through examination of these plots, the geologist can quickly separate samples into natural groupings (Figure 3). Because permeability directly reflects fluid flow capacity, it is the major parameter used to designate reservoir rock categories. Because porosity is commonly a major control on permeability, it generally exhibits a positive correlation with that variable. Attempts to create hierarchies of permeability heterogeneity based strictly on depositional criteria<ref name=Lewis, 1978>63rd Annual SPE Technical Conference Proceedings, p.449-463, SPE #18153</ref>  should be avoided in reservoirs where diagenetic alterations are major controls on permeability heterogeneity. If natural groupings are not present, it may be necessary to set arbitrary group boundaries, such as porosity or permeability cutoffs.

Estimation of the lateral distribution of zones is then guided by relationships developed in the integrated geological model and documented in the form of maps and cross sections.

Estimation of the lateral distribution of zones is then guided by relationships developed in the integrated geological model and documented in the form of maps and cross sections.

===Stage 6. Applications studies===

===Stage 6. Applications studies===

Depending on the objectives of the study being conducted, the geologist needs to generate additional maps, cross sections, fence diagrams, or simulation models. For the purposes of reserve estimation, net pay maps are needed (see “[[Effective pay determination]]”). If the major controls on net pay distribution are diagenetic in nature, contouring of net pay maps should be guided by trends present on contour maps of major diagenetic components. Average porosity maps should also be “guided” in this same fashion. Where simulation of fluid flow behavior is the object of the study, the geologist must assist in the preparation of a three-dimensional simulation model.

Depending on the objectives of the study being conducted, the geologist needs to generate additional maps, cross sections, fence diagrams, or simulation models. For the purposes of reserve estimation, net pay maps are needed (see [[Effective pay determination]]). If the major controls on net pay distribution are diagenetic in nature, contouring of net pay maps should be guided by trends present on contour maps of major diagenetic components. Average porosity maps should also be “guided” in this same fashion. Where simulation of fluid flow behavior is the object of the study, the geologist must assist in the preparation of a three-dimensional simulation model.

===Stage 7. Model testing and revision===

===Stage 7. Model testing and revision===

Where economics dictate, it may be necessary to test the accuracy of the models developed. This can include testing by history matching of pressures, production rates, and GOR values for segments of the model or full scale testing of the complete model<ref name=pt06r155>Weber, K. J., Klootwijk, P. H., Knoieczek, J., van der Vlugt, W. R., 1978, Simulation of water injection in a barrier-bar- type, oil-rim reservoir in Nigeria: Journal of Petroleum Technology, v. 30, p. 1555–1565., 10., 2118/6702-PA</ref> (see “Product Histories”) and “Conducting a Reservoir Simulation Study: An Overview” in Part 10). Testing can also involve drilling additional wells, conducting special engineering tests (pulse or tracer), and collecting geological data on additional samples. Revisions may also be required as additional wells, particularly infill wells, are drilled in the field.

Where economics dictate, it may be necessary to test the accuracy of the models developed. This can include testing by history matching of pressures, production rates, and GOR values for segments of the model or full scale testing of the complete model<ref name=pt06r155>Weber, K. J., Klootwijk, P. H., Knoieczek, J., van der Vlugt, W. R., 1978, Simulation of water injection in a barrier-bar- type, oil-rim reservoir in Nigeria: Journal of Petroleum Technology, v. 30, p. 1555–1565., 10., 2118/6702-PA</ref> (see [[Product histories]] and [[Conducting a reservoir simulation study: an overview]]). Testing can also involve drilling additional wells, conducting special engineering tests (pulse or tracer), and collecting geological data on additional samples. Revisions may also be required as additional wells, particularly infill wells, are drilled in the field.

==See also==

==See also==