bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inferring Interwell Connectivity from Well Bottomhole-Pressure Fluctuations in Waterfloods
Authors: Dinh Anh , Tiab Djebbar 
Published: November 2008

SummaryThis paper presents a new procedure to determine interwell connectivity in a reservoir on the basis of fluctuations of bottomhole pressure of both injectors and producers in a waterflood. The method uses a constrained multivariate linear-regression (MLR) analysis to obtain information about permeability trends, channels, and barriers.Previous authors applied the same analysis to injection and production rates to infer connectivity between wells. In order to obtain good results, however, they applied various diffusivity filters to the flow-rate data to account for the time lags and the attenuation. This was a tedious process that requires subjective judgment. Shut-in periods in the data, usually unavoidable when a large number of data points were used, created significant errors in the results and were often eliminated from the analysis.This new method yielded better results compared with the results obtained when production data were used. Its advantages include: (1) no diffusivity filters needed for the analysis, (2) minimal number of data points required to obtain good results, (3) and flexible plan to collect data because all constraints can be controlled at the surface. The new procedure was tested by use of a numerical reservoir simulator. Thus, different cases were run on two fields, one with five injectors and four producers and the other with 25 injectors and 16 producers.For a large waterflood system, multiple wells are present and most of them are active at the same time. In this case, pulse tests or interference tests between two wells are difficult to conduct because the signal can be distorted by other active wells in the reservoir. In the proposed method, interwell connectivity can be obtained quantitatively from multiwell pressure fluctuations without running interference tests.
A Practical Iterative Scheme for Coupling Geomechanics With Reservoir Simulation
Authors: Samier Pierre , Onaisi Atef , de Gennaro Sergio 
Published: November 2008

Summary
The use of reservoir simulation coupled with geomechanics has been increasing in recent years as its utility in modeling physical phenomena such as compaction, subsidence, induced fracturing, enhancement of natural fractures and/or fault activation, and steam-assisted gravity drainage (SAGD) recovery has become apparent. Among different methods investigated by researchers, the iterative explicit method appears to be the preferred method for field-scale simulation.
This method is a loose coupled approach between a reservoir simulator and a geomechanical simulator. At user-defined steps, the fluid pressures are transmitted to the geomechanical tool, which computes the actual stresses and reports the modifications of porosities and permeabilities back to the reservoir simulator.
This paper presents a new iterative scheme that allows any reservoir simulator to be coupled with any nonlinear finite-element-method (FEM) package for the stress analysis without any limitation on the functionality of either simulator. The convergence of this new scheme is discussed, and results are presented for three cases described below.
The first case is a validation case used by other SPE papers. The second case is a synthetic model of a highly compacting reservoir sensitive to water saturation. The third case is a full-field reservoir model.
Managing Formation-Damage Risk From Scale-Inhibitor Squeeze Treatments in Deepwater, Subsea Fields in the Campos Basin
Authors: Bogaert Philip , Berredo Marcos C. , Toschi Celso , Bryson Bill , Jordan Myles M. , Frigo Dario M. , Afonso Marcos 
Published: November 2008

Summary
This paper describes field experience and lessons learned from bullhead-deployed scale-control operations in a deepwater subsea development in the Campos basin, Brazil; specifically, this paper is about deploying such treatments from the floating production, storage, and offloading (FPSO) host, along the production flow-lines, and into four low-water-cut, horizontal, subsea wells completed with sand control.
The relatively small number of high-cost, highly productive wells, coupled with a very high barium sulfate (BaSO4) scaling tendency upon breakthrough of injection water, meant that not only was effective downhole scale management critical to achieve high hydrocarbon recovery, but that even wells at low water cuts were deemed to be at sufficient risk to require squeeze application.
Initial bullheaded scale treatments comprised three "hybrid" treatments: a mutual-solvent preflush, a water-based main flush, and a diesel overflush. As water-production rates rose, so did the treatment volumes required. To improve the logistics of these treatments and to mitigate issues that arise from poor injectivity of diesel in these wells, core studies were conducted to investigate the option of changing the overflush fluid from marine diesel to injection-quality seawater. This change also introduced the possibility of forming a gas-hydrate plug during shut-in, but this was managed by use of a thermodynamic hydrate inhibitor and by replacing the flowline contents to flashed crude during the shut-in period. Both the operational aspects and the response of the wells to the modified treatments will be compared with those previously deployed in terms of, in particular, the injectivity of the wells during treatment and well-treatment cleanup rates and productivity afterward.
The core studies also highlighted a formation-damage mechanism caused by incompatibility between the mutual solvent and the produced oil; this required modification of the treatment.
Effect of Droplet Size, Emulsifier Concentration, and Acid Volume Fraction on the Rheological Properties and Stability of Emulsified Acids
Authors: Al-Mutairi S. H. , Hill A. D. , Nasr-El-Din H. A. 
Published: November 2008

Summary
Acid-in-diesel emulsions have been used extensively in matrix-acidizing and acid-fracturing treatments. This acid has several advantages, including lower corrosion rate, minimum number of additives, and deep acid penetration. For stimulation purposes, the most important properties of emulsified acid are reactivity, stability, and viscosity. The size distribution of the droplets of the emulsion affects these properties.
The purpose of this paper is to correlate the droplet size of the dispersed phase (acid) to the viscosity and stability of emulsified acids. Measurements of the droplet size were acquired with laser-diffraction techniques and analyzed by use of an advanced image-processing system. The apparent viscosity was measured with a Brookfield PVS rheometer at various temperatures. The stability of the emulsified acid was monitored by use of an HTHP see-through cell.
Steady shear viscosity was measured for emulsions with droplet sizes ranging in diameter from 1 to 20 μm. The viscosity covered a shear rate range from 10 to 750 s−1 and a temperature range from 25 to 80°C. All measurements were regenerated for emulsifier concentrations of 1, 5, and 10 gpt. It was noted that finer emulsions had higher viscosities. Likewise, similar measurements were performed with varying acid volume fractions.
The most stable emulsion was noted at an acid volume fraction of nearly 0.7. Other volume fractions were stable for a few hours before diesel was expelled as a separate layer above the emulsion. Eventually, the remaining emulsion stabilized at an acid volume fraction of 0.7.
This paper discusses the effects of the acid volume fraction, emulsifier concentration, and droplet size distribution on the rheological properties and stability of emulsified acids.
Improving Reserves Estimates From Decline-Curve Analysis of Tight and Multilayer Gas Wells
Authors: Cheng Y. , Lee W. J. , McVay D. A. 
Published: November 2008

SummaryDecline-curve analysis is one of the most commonly used techniques to estimate reserves from production data. In tight formations that have been stimulated—especially when there are multiple layers that communicate only at the wellbore—the uncertainty in reserves estimates from this technique is quite large because forecasting future performance is quite difficult. This uncertainty can affect the classification of reserves, and could limit what we should call "proved developed reserves." In this paper, we present new procedures to mitigate the complexity of decline-curve analysis in multilayer tight gas wells. Using synthetic and field examples, we demonstrate how reserves can be estimated more reliably.For tight and multilayer gas wells, it is not uncommon that decline-curve analysis yields an Arps decline-curve parameter b greater than unity (Arps 1945). Single-layer hydraulically fractured tight gas wells also appear to have b-values greater than unity. Different practices are used to handle such complexity. For forecasts, some analysts simply use the b-value obtained from matching production data, while others force the b value to be unity. Still others use the hyperbolic decline and the matched value of b, but, when the decline rate reaches a predetermined limit, they switch to exponential decline for the remainder of the forecast. Thus, forecasted performance differs significantly when different analysts analyze the data. Consequently, the reserves estimate has large uncertainty, which can, in turn, affect its classification.In this paper, we first present an in-depth investigation of decline behavior of tight, single-layer and multilayer gas wells by analyzing depletion characteristics using simulated data sets. We illustrate the long-duration transient effects present in single-layer stimulated tight gas wells and the complex flow regimes present when wells in layered reservoirs are produced commingled. Our work indicates that, as observed in field data, transient effects and coexistence of different flow regimes between layers lead to abnormal decline behavior (b &gt; 1.0) in multilayer tight gas wells, which leads to errors in production forecasts. Our new procedure provides a method to minimize these errors.
Plugging of Fractures in Chalk Reservoirs by Enzyme-Induced Calcium Carbonate Precipitation
Authors: Larsen Jan , Poulsen Mikael , Lundgaard Thomas , Agerbæk Mikkel 
Published: November 2008

Summary
Natural or induced fractures in a chalk reservoir can reduce the recovery of an oil field significantly. Therefore, the plugging of fractures with a wide range of materials has been investigated over the years. Calcium carbonate is an obvious candidate, being the main constituent of the reservoir itself. However, to apply calcium carbonate as a plugging fluid, a mechanism is required for delaying the precipitation until the chemical reaches the fracture. An enzymatically induced plugging mechanism has been suggested, in which the urease enzyme converts urea into ammonia and carbonate. This carbonate will then precipitate with calcium as calcium carbonate. However, the amount of calcium carbonate produced was relatively low and the cost of the stabilizer and high-purity-enzyme source was prohibitively high for practical use. Furthermore, the calcium carbonate precipitated as a slurry of small particles, which is deemed less efficient for fracture plugging when compared to larger crystals or aggregates.
In this paper, work is presented on design of an improved plugging fluid based on enzymatic calcium-carbonate precipitation and optimization toward a field-applicable solution. The relatively expensive stabilizer and enzyme source are replaced with low-cost ingredients, and the rate of precipitation is improved. By optimizing the concentrations of the reactants, we have improved the yield of calcium carbonate from 20 to more than 200 g/L. Furthermore, the crystallization can be controlled to obtain much larger calcium carbonate crystals. Laboratory plugging experiments have shown that larger crystal sizes improve the durability of the formed plugs significantly.
On Interfacial-Tension Measurements to Estimate Minimum Miscibility Pressures
Authors: Jessen Kristian , Orr Franklin M. 
Published: November 2008

Summary
Measurements of the interfacial1 tension (IFT) of mixtures of a reservoir fluid and injection gas at various pressures have been proposed as an experimental method for predicting the minimum miscibility pressure (MMP) in an experiment referred to as the vanishing-IFT (VIT) technique. In this paper, we analyze the accuracy and reliability of the VIT approach using phase equilibrium and slimtube experimental observations and equation-of-state (EOS) calculations of the behavior of VIT experiments for the same systems.
We consider 13 gas/oil systems for which phase equilibrium and density data and slimtube measurements of the MMP are available. We show that tuned EOS characterizations using 15 components to represent the gas/oil systems yield calculations of phase compositions and densities and calculated MMPs that reproduce the experimental observations accurately. We assume that IFTs can be calculated with a parachor expression, and we simulate the behavior of a series of VIT experiments with different mixture compositions in the VIT cell. We show that compositions of mixtures created in the VIT cell are not, in general, critical mixtures and that calculated estimates of the MMP obtained by the VIT approach depend strongly on the composition of the mixture used in the experiment. We show also that those MMP estimates may or may not differ significantly from values obtained in slim-tube displacements. Fortuitously chosen mixture compositions can result in VIT-experiment estimates that agree well with slimtube MMPs, while for other mixtures, the error of the estimates can be quite large. In particular, we show that errors in the VIT-technique estimate of the MMP are often large for gas/oil systems for which the first-contact miscibility pressure (FCMP) is much larger than the slimtube MMP.
We conclude, therefore, that the VIT experiment is not a reliable single source of information regarding the development of multicontact miscibility in multicomponent gas/oil displacements.
Recognition of Human Proinsulin Leader Sequence by Class I–Restricted T-Cells in HLA-A*0201 Transgenic Mice and in Human Type 1 Diabetes
Authors: Toma Andréa , Laïka Taghrid , Haddouk Samy , Luce Sandrine , Briand Jean-Paul , Camoin Luc , Connan Francine , Lambert Marion , Caillat-Zucman Sophie , Carel Jean-Claude , Muller Sylviane , Choppin Jeannine , Lemonnier François , Boitard Christian 
Published: November 2008

OBJECTIVE— A restricted region of proinsulin located in the B chain and adjacent region of C-peptide has been shown to contain numerous candidate epitopes recognized by CD8+ T-cells. Our objective is to characterize HLA class I–restricted epitopes located within the preproinsulin leader sequence.RESEARCH DESIGN AND METHODS— Seven 8- to 11-mer preproinsulin peptides carrying anchoring residues for HLA-A1, -A2, -A24, and -B8 were selected from databases. HLA-A2–restricted peptides were tested for immunogenicity in transgenic mice expressing a chimeric HLA-A*0201/β2-microglobulin molecule. The peptides were studied for binding to purified HLA class I molecules, selected for carrying COOH-terminal residues generated by proteasome digestion in vitro and tested for recognition by human lymphocytes using an ex vivo interferon-γ (IFN-γ) ELISpot assay.RESULTS— Five HLA-A2–restricted peptides were immunogenic in transgenic mice. Murine T-cell clones specific for these peptides were cytotoxic against cells transfected with the preproinsulin gene. They were recognized by peripheral blood mononuclear cells (PBMCs) from 17 of 21 HLA-A2 type 1 diabetic patients. PBMCs from 25 of 38 HLA-A1, -A2, -A24, or -B8 patients produced IFN-γ in response to six preproinsulin peptides covering residues 2–25 within the preproinsulin region. In most patients, the response was against several class I–restricted peptides. T-cells recognizing preproinsulin peptide were characterized as CD8+ T-cells by staining with peptide/HLA-A2 tetramers.CONCLUSIONS— We defined class I–restricted epitopes located within the leader sequence of human preproinsulin through in vivo (transgenic mice) and ex vivo (diabetic patients) assays, illustrating the possible role of preproinsulin-specific CD8+ T-cells in human type 1 diabetes.
Exenatide Sensitizes Insulin-Mediated Whole-Body Glucose Disposal and Promotes Uptake of Exogenous Glucose by the Liver
Authors: Zheng Dan , Ionut Viorica , Mooradian Vahe , Stefanovski Darko , Bergman Richard N. 
Published: November 2008

OBJECTIVE— Recent progress suggests that exenatide, a mimetic of glucagon-like peptide-1 (GLP-1), might lower glycemia independent of increased β-cell response or reduced gastrointestinal motility. We aimed to investigate whether exenatide stimulates glucose turnover directly in insulin-responsive tissues dependent or independent of insulinemia.
RESEARCH DESIGN AND METHODS— An intraportal glucose infusion clamp was used in dogs to measure glucose turnover to encompass potent activation of the putative glucose/GLP-1 sensor in the porto-hepatic circulation with exenatide. The modified glucose clamp was performed in the presence of postprandial hyperinsulinemia and hyperglycemia with exenatide (20 μg) or saline injected at 0 min. Furthermore, the role of hyperglycemia versus hyperinsulinemia in exenatide-mediated glucose disposal was studied.
RESULTS— With hyperinsulinemia and hyperglycemia, exenatide produced a significant increase in total glucose turnover by ∼30%, as indicated by portal glucose infusion rate (saline 15.9 ± 1.6 vs. exenatide 20.4 ± 2.1 mg · kg−1 · min−1, P &lt; 0.001), resulting from increased whole-body glucose disposal (Rd, ∼20%) and increased net hepatic uptake of exogenous glucose (∼80%). Reducing systemic hyperglycemia to euglycemia, exenatide still increased total glucose turnover by ∼20% (saline 13.2 ± 1.9 vs. exenatide 15.6 ± 2.1 mg · kg−1 · min−1, P &lt; 0.05) in the presence of hyperinsulinemia, accompanied by smaller increments in Rd (12%) and net hepatic uptake of exogenous glucose (45%). In contrast, reducing hyperinsulinemia to basal levels, exenatide-increased total glucose turnover was completely abolished despite hyperglycemia (saline 2.9 ± 0.6 vs. exenatide 2.3 ± 0.3 mg · kg−1 · min−1, P = 0.29).
CONCLUSIONS— Exenatide directly stimulates glucose turnover by enhancing insulin-mediated whole-body glucose disposal and increasing hepatic uptake of exogenous glucose, contributing to its overall action to lower postprandial glucose excursions.
Effectiveness of drotaverine hydrochloride in progression of labour
Authors: Thapa Meena , Saha Rachana , Pradhan Amita , Shrestha Sweety 
Published: November 2008

Aim: This study was done to compare the effectiveness of drotaverine hydrochloride and valethamate bromide in shortening duration of labour. Methods: It is a hospital based prospective study, carried out in the department of Obstetrics & Gynaecology at Kathmandu Medical College Teaching Hospital (KMCTH), Sinamangal from 1st June to 31st August 2005. 99 patients, who were in active labour, were taken into the study. Out of which 50 were in drotaverine group (Group 1) who had received 40 mg of drotaverine hydrochloride intramuscularly at 3 to 5 cm dilatation of the cervix. Rest of 49 patients were in valethamate bromide group (Group 2). They received 3 doses of 8 mg valethamate bromide and 20 mg hyoscin butyl bromide intravenously half an hour interval. Result: The injection-delivery interval was studied in both Groups. The duration of injection-delivery interval was found to be almost equal in primigravidae of both Groups (p=0.72). But in multigravidae interval was significantly shorter in drotaverine Group (p=0.03). Conclusion: Both drotaverine and valethamate bromide are equally effective in shortening duration labour in primigravidae, where as drotaverine is more effective in multigravidae in accelerating labour. Keywords: Drotaverine, Valethamate bromide, cervical dilatation, labour acceleration doi:10.3126/njog.v2i2.1447 N. J. Obstet. Gynaecol 2007 Nov-Dec; 2 (2): 9 - 11
Intraperitoneal haemorrhage- A call for laparotomy as second intervention
Authors: Rawal Suniti , Rana Ashma , Bista Kesang D , Gurung Geeta , Ghimire Ram K 
Published: November 2008

Aim: To study laparotomy as second intervention for hemoperitoneum following primary surgery in obstetric and gynecology. Method: Eleven years retrospective study going back from Dec 2006 embracing all the cases of re/laparotomy for intraperitoneal bleeding were carried out in TUTH, Nepal. Results: Of the 24 cases complicated by intraperitoneal hemorrhage for which relaparotomy had been done 12 each were formed by gynaecologic and obstetric cases: 11 were caesareans (CS) and a laparotomy following vaginal birth after caesarean (VBAC). In gynecology the preceding surgeries undertaken were [diagnostic laparoscopy (1), laparotomy (3), hysterectomies 8 (3 being vaginal)] Massive hemoperitoneum occurred in ¼ cases; extensive hematoma in a third having altogether with associated risks factor in 9(37.5%).Source of bleeding were disligated/abraded infundibulopelvic vessel (3), cuff bleeding (4), cardinal ligaments (1), uterine cornua (1), uterine angles (6), vagina (1) and placental bed (1) which were duly managed by 5 obstetrics hysterectomy. Laparotomy >2 times were repeated 4: obstetric 2 [(1) for vault bleeding following hysterectomy done for scar rupture after VBAC and other for slippage of ovarian vessel following hysterectomy and internal iliac ligation] and same number in Gynecology 2 [(1) after vaginal hysterectomy first for laceration of infundibulopelvic vessel and then for generalized ooze and hematoma]. Next was following a diagnostic laparoscopy, complicated by unexplainable intraperitoneal bleeding first devised by internal iliac ligation, then finally by hysterectomy that died. Conclusions: Careful tying of the blood vessel, choosing right technique and appropriate ligature in the first place is as important as proper closure of all the surgical incision/ inflicted cut taking note of the rise in the pulse rate and fall in the blood pressure in overall postoperative cases such that related morbidity and mortality from late diagnosis leading to delayed second surgical intervention can be obviated or minimized. Key Words: Intraperitoneal bleeding, hemoperitoneum, relaparotomy doi:10.3126/njog.v2i2.1458 N. J. Obstet. Gynaecol 2007 Nov-Dec; 2 (2): 63 - 68
Unexplained hemolytic anemia of pregnancy: Case report with review of related literature
Authors: Sharma Paban , Sthapit Rekha 
Published: November 2008

We present a case of a multipara lady who developed hemolytic anemia during pregnancy with spontaneous remission after delivery. She was managed with low dose steroid for hemolysis during pregnancy with good feto-maternal outcome. Despite extensive investigations carried out to determine the cause, they remained in vain. Very few of such cases have been described in the literature, which merits its presentation. Key words: Hemolytic anemia, pregnancy doi:10.3126/njog.v3i1.1441 NJOG 2008 May-June; 3(1): 49 - 50