Numerical RTA in Tight Unconventionals

We extend the numerically-assisted RTA workflow proposed by Bowie and Ewert (2020) to (a) all fluid systems and (b) finite conductivity fractures. The simple, fully-penetrating planar fracture model proposed is a useful numerical symmetry element model that provides the basis for the work presented in this paper. Results are given for simulated and field data. The linear flow parameter (LFP) is modified to include porosity (LFPꞌ=LFP√φ). The original (surface) oil in place (OOIP) is generalized to represent both reservoir oil and reservoir gas condensate systems, using a consistent initial total formation volume factor definition (Bti) representing the ratio of a reservoir HCPV containing surface oil in a reservoir oil phase, a reservoir gas phase, or both phases. With known (a) well geometry, (b) fluid initialization (PVT and water saturation), (c) relative permeability relations, and (d) bottomhole pressure (BHP) time variation (above and below saturation pressure), three fundamental relationships exist in terms of LFPꞌ and OOIP. Numerical reservoir simulation is used to define these relationships, providing the foundation for numerical RTA, namely that wells: (1) with the same value of LFPꞌ, the gas, oil and water surface rates will be identical during infinite-acting (IA) behavior; (2) with the same ratio LFPꞌ/OOIP, producing GOR and water cut behavior will be identical for all times, IA and boundary dominated (BD); and (3) with the same values of LFPꞌ and OOIP, rate performance of gas, oil, and water be identical for all times, IA and BD. These observations lead to an efficient, semi-automated process to perform rigorous RTA, assisted by a symmetry element numerical model. The numerical RTA workflow proposed by Bowie and Ewert solves the inherent problems associated with complex superposition and multiphase flow effects involving time and spatial changes in pressure, compositions and PVT properties, saturations, and complex phase mobilities. The numerical RTA workflow decouples multiphase flow data (PVT, initial saturations and relative permeabilities) from well geometry and petrophysical properties (L, xf, h, nf, φ, k), providing a rigorous yet efficient and semi-automated approach to define production performance for many wells. Contributions include a technical framework to perform numerical RTA for unconventional wells, irrespective of fluid type. A suite of key diagnostic plots associated with the workflow is provided, with synthetic and field examples used to illustrate the application of numerical simulation to perform rigorous RTA. Semi-analytical models, time, and spatial superposition (convolution), pseudopressure and pseudotime transforms are not required.

Tetraphenylphosphonium tetrakis(trimethylsilanolato)ferrate(III)

The structure of tetraphenylphosphonium tetrakis(trimethylsilanolato)ferrate(III), [(C6H5)4P][Fe(OSi(CH3)3)4], has tetragonal (I-4) symmetry, and was refined as an inversion twin. It is an ionic compound consisting of a tetraphenylphosphonium cation and a tetrakis(trimethylsilanolato)ferrate(III) anion. The crystal structure comprises the two ionic species each centered on a -4 symmetry element and contributing a fourth of its structure to the asymmetric unit. Each is surrounded by counter-ions on all sides. The cation contains a central phosphorous atom bound to four phenyl groups in a tetrahedral arrangement, while the anion contains a central iron(III) atom tetrahedrally coordinated by four trimethylsilanolato ligands.

Synthesis and crystal structures of two structurally related kryptoracemates

Kryptoracemates are racemic compounds (pairs of enantiomers) that crystallize in Sohnke space groups (space groups that contain neither inversion centres nor mirror or glide planes nor rotoinversion axes). Thus, the two symmetry-independent molecules cannot be transformed into one another by any symmetry element present in the crystal structure. Usually, the conformation of the two enantiomers is rather similar if not identical. Sometimes, the two enantiomers are related by a pseudosymmetry element, which is often a pseudocentre of inversion, because inversion symmetry is thought to be favourable for crystal packing. We obtained crystals of two kryptoracemates of two very similar compounds differing in just one residue, namely rac-N-[(1S,2R,3S)-2-methyl-3-(5-methylfuran-2-yl)-1-phenyl-3-(pivalamido)propyl]benzamide, C27H32N2O3, (I), and rac-N-[(1S,2S,3R)-2-methyl-3-(5-methylfuran-2-yl)-1-phenyl-3-(propionamido)propyl]benzamide dichloromethane hemisolvate, C25H28N2O3·0.5CH2Cl2, (II). The crystals of both compounds contain both enantiomers of these chiral molecules. However, since the space groups [P212121 for (I) and P1 for (II)] contain neither inversion centres nor mirror or glide planes nor rotoinversion axes, there are both enantiomers in the asymmetric unit, which is a rather uncommon phenomenon. In addition, it is remarkable that (II) contains two pairs of enantiomers in the asymmetric unit. In the crystal, molecules are connected by intermolecular N—H...O hydrogen bonds to form chains or layered structures.

Crystallographic data of double antisymmetry space groups

This paper presents crystallographic data of double antisymmetry space groups, including symmetry-element diagrams, general-position diagrams and positions, with multiplicities, site symmetries, coordinates, spin vectors, roto vectors and displacement vectors.

Tetrakis(μ3-2-{[1,1-bis(hydroxymethyl)-2-oxidoethyl]iminomethyl}-6-nitrophenolato)tetracopper(II)

The title cluster, [Cu4(C11H12N2O6)4], was obtained from the Cu0–FeCl2·4H2O–H4L–Et3N–DMF reaction system (in air), where H4Lis 2-hydroxymethyl-2{[(2-hydroxy-3-nitrophenyl)methylidene]amino}propane-1,3-diol and DMF is dimethylformamide. The asymmetric unit consists of one Cu2+ion and one dianionic ligand; a -4 symmetry element generates the cluster, which contains a {Cu4O4} cubane-like core. The metal ion has an elongated square-based pyramidal CuNO4coordination geometry with the N atom in a basal site. An intramolecular O—H...O hydrogen bond is observed. The solvent molecules were found to be highly disordered and their contribution to the scattering was removed with the SQUEEZE procedure inPLATON[Spek (2009).Acta Cryst. D65, 148–155], which indicated a solvent cavity of volume 3131 Å3containing approximately 749 electrons. These solvent molecules are not considered in the given chemical formula.

Triprolidinium dichloranilate–chloranilic acid–methanol–water (2/1/2/2)

In the triprolidinium cation of the title compound {systematic name: 2-[1-(4-methylphenyl)-3-(pyrrolidin-1-ium-1-yl)prop-1-en-1-yl]pyridin-1-ium bis(2,5-dichloro-4-hydroxy-3,6-dioxocyclohexa-1,4-dien-1-olate)–2,5-dichloro-3,6-dihydroxycyclohexa-2,5-diene-1,4-dione–methanol–water (2/1/2/2)}, C19H24N22+·2C6HCl2O4−·0.5C6H2Cl2O4·CH3OH·H2O, the N atoms on both the pyrrolidine and pyridine groups are protonated. The neutral chloranilic acid molecule is on an inversion symmetry element and its hydroxy H atoms are disordered over two positions with site-occupancy factors of 0.53 (6) and 0.47 (6). The methanol solvent molecule is disordered over two positions in a 0.836 (4):0.164 (4) ratio. In the crystal, N—H...O, O—H...O and C—H...O interactions link the components. The crystal structure also features π–π interactions between the benzene rings [centroid–centroid distances = 3.5674 (15), 3.5225 (15) and 3.6347 (15) Å].