![]() ![]() It is used to show locations in a UTM coordinate system and display MGRS-specific information, such as 100,000-meter grid designators. Military Grid Reference System (MGRS) grid is a special type of measured grid. Learn more about how to use measured grids. They are used to show location using projected coordinates. ![]() Measured gridĪ measured grid is a network of evenly spaced horizontal and vertical lines used to identify locations on a map. They are used to show location in geographic coordinates (degrees of latitude and longitude). Graticules are lines showing parallels of latitude and meridians of longitude for the earth. Grids are used to show coordinates or divide the map frame. Most runs were performed to 4,475 days, which corresponds to about four hydrocarbon PV's of steam injected, defined as volume of steam (CWE) injected divided by initial volume of hydrocarbon-occupied pore space.There are five types of grids that can be added to a map frame: graticules, measured grids, MGRS grids, reference grids, and custom grids. The relative permeability endpoints and exponents listed in Table 1 were used in analytical expressions for relative permeability. ![]() The simulator places appropriate multiplicative (time-varying) mobilities for all phases on these productivity indices. Well-productivity indices in the pattern element runs were obtained as described in the Appendix and have units of RB-cp/day-psi. the production wells were placed on deliverability against a BHFP of 50 psia with no maximum or limiting production rate specified. Similarly, individual well production rates are reported as full well rates. Production rates for the pattern are reported on a full-pattern basis regardless of whether a 1/8, 1/4, 1/12, etc., pattern element is actually being simulated. Injection rate is 187.5 B/D of steam per pattern at 400 deg. However, no single data set should be considered representative of any particular reservoir. Various fluid and reservoir properties of these data sets are representative of various heavy-oil deposits in the U.S. The results presented were obtained for the three data sets of Table 1. This feature is coded for the five-point D4 Gauss ordering, the ordinary Gauss ordering used in the nine-point scheme, and the iterative solution technique ordering. For n such wells, this feature introduces n additional variables and n additional constraint equations into the matrix of equations requiring solution. ![]() An implicit bottomhole pressure (BHP) feature exactly preserves specified rates for wells not on deliverability or constraints (e.g., maximum steam production rate). Alterations of transmissibilities necessary to run 1/8 symmetry elements of (areally) homogeneous five- and nine-spot patterns are included in the model for five- and nine-point difference schemes with uniform or variable grid spacing. This nine-point scheme is coded in the planes for areal or three-dimensional (3D) problems and in the x-z plane for 2D cross sections. The nine-point difference scheme is an option in addition to the conventional five-point scheme. We will briefly discuss only the additional features pertinent to the results presented in this paper. While the basic formulation and PVT representation are unchanged, a large number of features have been added. The thermal model we used is extended considerably beyond a model previously described. Subject to certain conditions, the paper presents a simple procedure to calculate well-productivity indices for uniform or nonuniform grids, cross sections, or any of the three patterns, and either of the two difference schemes. This is important because of significantly reduced cost compared with 1/4- or 1/2-pattern elements. Nine-point transmissibility alterations are used that allow rigorous use of 1/8 five-/nine-spot patterns as opposed to 1/2 or 1/4 elements with either parallel or diagonal grids. The conclusions emphasize superiority of the nine-point difference scheme and the pitfalls of certain problem/grid/difference-scheme combinations in pattern steamflood simulation. Various seven-spot grids (neither parallel nor diagonal) and nonuniform five-/nine-spot grids pose unique challenges to both difference schemes, with interesting results. Sample problem data sets are roughly representative of a California deposit and a more viscous Alberta crude. Effects of different types of grid spacings in cyclic steam simulation are discussed. The effects of difference scheme and grid orientation are examined in a two-dimensional (2D) (vertical) cross section. This paper presents five-, seven-, and nine-spot pattern steamflood simulation results with parallel and diagonal grids and five- and nine-point difference schemes. ![]()
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