![]() ![]() ![]() With Cartesian space this is not guaranteed. Whatever program you use should automatically recognize the constraint and will optimize your molecule accordingly giving you an answer based off a structure that is constrained to C2v symmetry. You would construct your Z-matrix to define the OH(1) bond as being equivalent to the OH(2) bond. With a Z-matrix, the process is very straightforward. When using some sort of optimizing routine, you may want to specify symmetry in your system. The OH bond lengths should be equivalent. We know from experience that this molecule has C2V symmetry. When performing complex computations, the less you have to keep track of, the less expensive the computation.Ĭonsider the following molecule, H2O. For linear molecules we keep tabs on 3N-5 coordinates. ![]() Using internal coordinates reduces our 3N requirement set by the Cartesian space down to a 3N-6 requirement (for non-linear molecules). With Z-matrices, we keep tabs on internal coordinates: bond length (R), bond angle (A), and torsional/dihedral angle (T/D). We increased the distance between the two atoms by some length R. What did we change? We simply changed the bond length, one variable. We now have altered the molecule in such a way that the properties of that molecule has changed. However, say we increase the distance between the hydrogen atoms. ![]() An H2 molecule centered around the origin (0,0,0) is no different from the same H2 molecule being centered around (1,1,1). The translation of the molecule through space (assuming a vacuum) will have no affect on the properties of the molecule. A point located at (0,0,1) is an absolute location for a coordinate space that extends to infinity. Cartesian space is 'absolute' so to speak. When dealing with Z-matrices, we keep track of the relative positions of points in space. The general ruling is that for Cartesian space, 3N variables must be accounted for (where N is the number of points in space you wish to index). To describe the locations of two atomic nuclei, a total of 6 variables must be written down and kept track of. This paper summarises the key design aspects adopted to deliver successful matrix injection performance, presents the improvements implemented during offshore execution and provides an insight into the early life injection performance.In Cartesian space, three variables (XYZ) are used to describe the position of a point in space, typically an atomic nucleus or a basis function. Fieldwide injection commenced in July 2019 with favorable results. Filter cake clean up by means of flowback was discounted for GEP due to cost and the inability of some wells to naturally flow during early life.Īll GEP injection wells were completed in 2018-2019, one of which is globally the longest horizontal water injection well completed to date based on the Rushmore data base. While filter cake breakers have been previously used in the industry, they are typically combined with a flowback for filter cake removals. The GEP injection wells are a critical aspect of water flood design in a complex field, new to Woodside and with limited global benchmarks.Ī specific drilling and completion fluid system (Reservoir drilling fluid, completion fluid and chemical filter cake breaker) combined with a unique clean up and displacement technique have been adopted to provide high and sustainable matrix injection performance. Six water injection wells are required to provide pressure support and sweep oil to three production wells in the Laverda Canyon and Cimatti oil accumulations to improve oil recovery. The Greater Enfield Project (GEP) is a challenging offshore oil development, designed to produce from the Laverda Canyon, Cimatti and Norton over Laverda oil fields. ![]()
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