Immiscible and miscible gas-oil displacements in porous media

Gas Injection is the second largest EOR process in U.S. To increase the extent of the reservoir contacted by displacing fluids, gas and water are injected intermittently - water-alternating-gas (WAG) process, is widely practiced. This experimental study is aimed at evaluating the WAG process performance in short and long cores as a function of gas-oil miscibility and brine composition. This performance evaluation has been carried out by comparing oil recoveries between WAG injection and continuous gas injection (CGI). Miscible (2500 psi) and immiscible (500 psi) floods were conducted using Berea cores, n-Decane and two different brines, namely the commonly used 5% NaCl solution and another the multicomponent brine from the West Texas Yates reservoir. Each of the ten corefloods consisted of series of steps including brine saturation, absolute permeability determination, flooding with oil (drainage) to initial oil saturation, flooding with brine (imbibition) to residual oil saturation, and finally, tertiary gas injection to recover the waterflood residual oil. It was found that comparing tertiary gas floods only on the basis of recovery yielded misleading conclusions. However, when oil recovery per unit volume of gas injection was used as a parameter to evaluate the floods, miscible gas floods were found more effective (recovery 60-70% higher) than immiscible floods. The WAG mode of injection out-performed the CGI floods. At increased gas volume injection, the performance of miscible CGI flood, inspite of the high injection pressure, approached the immiscible floods. A change in brine composition from 5% NaCl to 9.26% multivalent Yates reservoir brine showed a slight adverse effect on tertiary gas flood recovery due to increased solubility of CO2 in the latter. While immiscible WAG floods in short cores donot show appreciable improvement over CGI immiscible floods, WAG recovery was 31% higher than 6-ft CGI floods. The results of this study prompted a new process by combining CGI and WAG modes of gas injection. Such a process was found patented and practiced in the industry. In addition to providing performance characteristics of the WAG process, this study has indicated directions for further research aimed at improving oil recovery from gas injection processes

On discreteness of subgroups of quaternionic hyperbolic isometries

Let ${{\bf H}_{\mathbb H}}^n$ denote the $n$-dimensional quaternionic hyperbolic space. The linear group ${\rm{Sp}}(n,1)$ acts by the isometries of ${{\bf H}_{\mathbb H}}^n$. A subgroup $G$ of ${\rm {Sp}}(n,1)$ is called \emph{Zariski dense} if it does not fix a point on ${{\bf H}_{\mathbb H}}^n \cup \partial {{\bf H}_{\mathbb H}}^n$ and neither it preserves a totally geodesic subspace of ${{{\bf H}}_{\mathbb H}}^n$. We prove that a Zariski dense subgroup $G$ of ${\rm{ Sp}}(n,1)$ is discrete if for every loxodromic element $g \in G$ the two generator subgroup $\langle f, g f g^{-1} \rangle$ is discrete, where the generator $f \in {\rm{Sp}}(n,1)$ is certain fixed element not necessarily from $G$.Comment: Reformatted, adding new result, and removing some. Removed parts will be subsumed elsewher

Green’s Function for a Slice of the Korányi Ball in the Heisenberg Group H

We give a representation formula for solution of the inhomogeneous Dirichlet problem on the upper half Korányi ball and for the slice of the Korányi ball in the Heisenberg group Hn by obtaining explicit expressions of Green-like kernel when the given data has certain radial symmetry

Wolbachia endosymbiont of the horn fly Haematobia irritans irritans: a supergroup A strain with multiple horizontally acquired cytoplasmic incompatibility genes

The horn fly, Haematobia irritans irritans, is a hematophagous parasite of livestock distributed throughout Europe, Africa, Asia, and the Americas. Welfare losses on livestock due to horn fly infestation are estimated to cost between USD 1-2.5 billion annually in North America and Brazil. The endosymbiotic bacterium Wolbachia pipientis is a maternally inherited manipulator of reproductive biology in arthropods and naturally infects laboratory colonies of horn flies from Kerrville, USA and Alberta, Canada, but has also been identified in wild-caught samples from Canada, USA, Mexico and Hungary. Re-assembly of PacBio long-read and Illumina genomic DNA libraries from the Kerrville H. i. irritans genome project allowed for a complete and circularised 1.3 Mb Wolbachia genome (wIrr). Annotation of wIrr yielded 1249 coding genes, 34 tRNAs, three rRNAs, and five prophage regions. Comparative genomics and whole genome Bayesian evolutionary analysis of wIrr compared to published Wolbachia genomes suggests that wIrr is most closely related to and diverged from Wolbachia supergroup A strains known to infect Drosophila spp. Whole-genome synteny analyses between wIrr and closely related genomes indicates that wIrr has undergone significant genome rearrangements while maintaining high nucleotide identity. Comparative analysis of the cytoplasmic incompatibility (CI) genes of wIrr suggests two phylogenetically distinct CI loci and acquisition of another CifB homolog from phylogenetically distant supergroup A Wolbachia strains suggesting horizontal acquisition of these loci. The wIrr genome provides a resource for future examination of the impact Wolbachia may have in both biocontrol and potential insecticide resistance of horn flies

Transinfection of buffalo flies (Haematobia irritans exigua) with Wolbachia and effect on host biology

Buffalo flies (Haematobia irritans exigua) (BF) and closely related horn flies (Haematobia irritans irritans) (HF) are invasive haematophagous parasites with significant economic and welfare impacts on cattle production. Wolbachia are intracellular bacteria found widely in insects and currently of much interest for use in novel strategies for the area wide control of insect pests and insect-vectored diseases. In this paper, we report the transinfection of BF towards the development of area-wide controls

Qualitative Grading as a Tool in the Management of Multilevel Lumbar Spine Stenosis

Study DesignThis is a prospective study that was undertaken at a single centre and involved 80 consecutive patients diagnosed with lumbar spinal stenosis (LSS).PurposeThe aim of the study was to assess the efficacy of a qualitative grading system as seen on magnetic resonance imaging (MRI) as a tool in the management of multilevel LSS.Overview of LiteratureLSS diagnosis is clinical but is usually radiologically supplemented. However, there are often multilevel radiological findings with non-specific or atypical clinical features. We used a qualitative grading system to help in the decision-making process of the management of patients with multilevel LSS.Methods80 patients with LSS were treated with decompression and prospectively followed-up for a minimum of 12 months. All had failed conservative treatment. Qualitative grading of LSS severity was based on the dural sac in T2 weighted axial MRI images at all disc levels and was done from L1–2 to L5–S1 (n=400). Functional outcome was assessed using the Oswestry disability index (ODI).ResultsThe mean patient age was 56.6 years, with a gender ratio of 0.6:1. Forty patients had degenerative LSS and 40 had degenerative spondylolysthesis. A total of 178 levels were decompressed, the majority of which were L4–L5 (43.82%), followed by L5–S1 (41.57%). According to our qualitative grading system, grade D stenosis (53.93%) was decompressed most frequently, followed by grade C stenosis (41.57%). The average preoperative ODI score was 58.55%, which later reduced to 19.15%. Seventy percent of patients achieved excellent results, whereas 30% achieved good results.ConclusionsMorphological grading is a useful tool in decision making in surgery for multilevel LSS. Grade C and D stenosis should be decompressed, whereas A and B should not be, unless clinically justified

Symbionts and gene drive: two strategies to combat vector-borne disease

Mosquitoes bring global health problems by transmitting parasites and viruses such as malaria and dengue. Unfortunately, current insecticide-based control strategies are only moderately effective because of high cost and resistance. Thus, scalable, sustainable, and cost-effective strategies are needed for mosquito-borne disease control. Symbiont-based and genome engineering-based approaches provide new tools that show promise for meeting these criteria, enabling modification or suppression approaches. Symbiotic bacteria like Wolbachia are maternally inherited and manipulate mosquito host reproduction to enhance their vertical transmission. Genome engineering-based gene drive methods, in which mosquitoes are genetically altered to spread drive alleles throughout wild populations, are also proving to be a potentially powerful approach in the laboratory. Here, we review the latest developments in both symbionts and gene drive-based methods. We describe some notable similarities, as well as distinctions and obstacles, relating to these promising technologies