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International audience; BACKGROUND: Patients who have had a stroke with unknown time of onset have been previously excluded from thrombolysis. We aimed to establish whether intravenous alteplase is safe and effective in such patients when salvageable tissue has been identified with imaging biomarkers. METHODS: We did a systematic review and meta-analysis of individual patient data for trials published before Sept 21, 2020. Randomised trials of intravenous alteplase versus standard of care or placebo in adults with stroke with unknown time of onset with perfusion-diffusion MRI, perfusion CT, or MRI with diffusion weighted imaging-fluid attenuated inversion recovery (DWI-FLAIR) mismatch were eligible. The primary outcome was favourable functional outcome (score of 0-1 on the modified Rankin Scale [mRS]) at 90 days indicating no disability using an unconditional mixed-effect logistic-regression model fitted to estimate the treatment effect. Secondary outcomes were mRS shift towards a better functional outcome and independent outcome (mRS 0-2) at 90 days. Safety outcomes included death, severe disability or death (mRS score 4-6), and symptomatic intracranial haemorrhage. This study is registered with PROSPERO, CRD42020166903. FINDINGS: Of 249 identified abstracts, four trials met our eligibility criteria for inclusion: WAKE-UP, EXTEND, THAWS, and ECASS-4. The four trials provided individual patient data for 843 individuals, of whom 429 (51%) were assigned to alteplase and 414 (49%) to placebo or standard care. A favourable outcome occurred in 199 (47%) of 420 patients with alteplase and in 160 (39%) of 409 patients among controls (adjusted odds ratio [OR] 1·49 [95% CI 1·10-2·03]; p=0·011), with low heterogeneity across studies (I(2)=27%). Alteplase was associated with a significant shift towards better functional outcome (adjusted common OR 1·38 [95% CI 1·05-1·80]; p=0·019), and a higher odds of independent outcome (adjusted OR 1·50 [1·06-2·12]; p=0·022). In the alteplase group, 90 (21%) patients were severely disabled or died (mRS score 4-6), compared with 102 (25%) patients in the control group (adjusted OR 0·76 [0·52-1·11]; p=0·15). 27 (6%) patients died in the alteplase group and 14 (3%) patients died among controls (adjusted OR 2·06 [1·03-4·09]; p=0·040). The prevalence of symptomatic intracranial haemorrhage was higher in the alteplase group than among controls (11 [3%] vs two [\textless1%], adjusted OR 5·58 [1·22-25·50]; p=0·024). INTERPRETATION: In patients who have had a stroke with unknown time of onset with a DWI-FLAIR or perfusion mismatch, intravenous alteplase resulted in better functional outcome at 90 days than placebo or standard care. A net benefit was observed for all functional outcomes despite an increased risk of symptomatic intracranial haemorrhage. Although there were more deaths with alteplase than placebo, there were fewer cases of severe disability or death. FUNDING: None.

Stroke thrombolysis with alteplase is currently recommended 0-4·5 h after stroke onset. We aimed to determine whether perfusion imaging can identify patients with salvageable brain tissue with symptoms 4·5 h or more from stroke onset or with symptoms on waking who might benefit from thrombolysis.In this systematic review and meta-analysis of individual patient data, we searched PubMed for randomised trials published in English between Jan 1, 2006, and March 1, 2019. We also reviewed the reference list of a previous systematic review of thrombolysis and searched ClinicalTrials.gov for interventional studies of ischaemic stroke. Studies of alteplase versus placebo in patients (aged ≥18 years) with ischaemic stroke treated more than 4·5 h after onset, or with wake-up stroke, who were imaged with perfusion-diffusion MRI or CT perfusion were eligible for inclusion. The primary outcome was excellent functional outcome (modified Rankin Scale [mRS] score 0-1) at 3 months, adjusted for baseline age and clinical severity. Safety outcomes were death and symptomatic intracerebral haemorrhage. We calculated odds ratios, adjusted for baseline age and National Institutes of Health Stroke Scale score, using mixed-effects logistic regression models. This study is registered with PROSPERO, number CRD42019128036.We identified three trials that met eligibility criteria: EXTEND, ECASS4-EXTEND, and EPITHET. Of the 414 patients included in the three trials, 213 (51%) were assigned to receive alteplase and 201 (49%) were assigned to receive placebo. Overall, 211 patients in the alteplase group and 199 patients in the placebo group had mRS assessment data at 3 months and thus were included in the analysis of the primary outcome. 76 (36%) of 211 patients in the alteplase group and 58 (29%) of 199 patients in the placebo group had achieved excellent functional outcome at 3 months (adjusted odds ratio [OR] 1·86, 95% CI 1·15-2·99, p=0·011). Symptomatic intracerebral haemorrhage was more common in the alteplase group than the placebo group (ten [5%] of 213 patients vs one [1%] of 201 patients in the placebo group; adjusted OR 9·7, 95% CI 1·23-76·55, p=0·031). 29 (14%) of 213 patients in the alteplase group and 18 (9%) of 201 patients in the placebo group died (adjusted OR 1·55, 0·81-2·96, p=0·66).Patients with ischaemic stroke 4·5-9 h from stroke onset or wake-up stroke with salvageable brain tissue who were treated with alteplase achieved better functional outcomes than did patients given placebo. The rate of symptomatic intracerebral haemorrhage was higher with alteplase, but this increase did not negate the overall net benefit of thrombolysis.None.

The prediction of thin interbed is an international problem in reservoir geophysics. This paper introduces the application of PP-PS joint inversion in thin shale interbeds prediction of the Junin field, Venezuela. Based on Petrophysical study, contact model with the effect of cementation is utilized to build the seismic rock physics model. S impedance and Vp/Vs were selected to be the sensitive elastic parameters to identify the shale interbeds in the unconsolidated sandstone reservoir. The PP-PS pre-stack joint inversion technology improves the accuracy of inversion result and distinguishes the thin shale interbeds effectively. Through statistics of 30 wells, it shows that 83% of the prediction matches the drilling results.

Cam is the key component of many important types of equipment. To improve the surface precision of cam, and to eliminate the cutter track, the production data format is analyzed in this paper, a conclusion that the big second derivative is the origin of track is reached. An algorithm to eliminate cutter track is brought forward, spline curve fitting is used to process the discreted data, and spline interpolation is used hereafter such that the second derivative is reduced to an acceptable range. The experiment shows that this method can efficiently eliminate the track on the surface, so as to improve the productivity of equipments.

The deposition of uniform, low-stress, thick and thin films of ultrananocrystalline diamond (UNCD) is investigated. The process methods and apparatus that enable the uniform and smooth deposition of both thin and thick (> 50 μm) UNCD across 3 in. diameters are described. UNCD films are synthesized by microwave plasma-assisted CVD using Ar/H 2 /CH 4 input gas mixtures over a wide pressure range (60–240 Torr) and temperature range (400–850 °C). Films were grown on 3 in. diameter silicon substrates with thicknesses ranging from 58 nm to greater than 50 μm. Film surface roughness as low as 10 nm (AFM) was obtained. Film uniformities of 70 to over 95% were achieved on 3 in. diameter silicon substrates. The growth rate increased as pressure, percent hydrogen and percent methane in the gas mixture, and microwave power increased. The highest growth rate 1.12 μm/h was achieved at 180 Torr, H 2 /Ar/CH 4 = (4:100:2) sccm and 1.5 kW absorbed power. Overall, a robust, repeatable process has been demonstrated for the deposition of UNCD films.

Surface acoustic wave (SAW) devices based on polycrystalline diamond have recently achieved success as microwave filters. This is due in part to the large acoustic wavelength of diamond at microwave frequencies, a consequence of its high surface wave velocity, and the resulting ability to use photolithography for transducer fabrication. Since nanocrystalline diamond has a smooth surface and is elastically isotropic, it may offer considerable advantages over thick films of polycrystalline diamond. We have studied the propagation of surface waves on nanocrystalline diamond prepared by microwave plasma chemical vapor deposition (CVD) on silicon substrates. Films were synthesized on 75-mm Si wafers using input gas mixtures consisting of Ar with 1% CH4 and 0–4% H2. The deposition parameters studied included pressure, 2.45 GHz microwave power, and total gas flow rate. Film thicknesses up to 23 μm were produced. SAW transducers were fabricated by photolithography on as-grown nanocrystalline diamond surfaces covered with a 1–3 μm overlayer of oriented polycrystalline piezoelectric ZnO prepared by reactive dc sputtering. The device response was analyzed with frequency and time domain methods. The resonant frequencies of the devices agree with the results of numerical solutions for sound propagation in layered media. Several surface acoustic modes exist at frequencies between 0.5 and 1 GHz that exhibit appreciable dispersion. We have propagated surface waves in nanocrystalline diamond over distances varying from 0.1 to 3 mm with low attenuation. For a film with mean grain size of approximately 30 nm, the SAW velocity is similar to test devices on thick polycrystalline diamond. We conclude that nanocrystalline diamond is a highly attractive substrate material for SAW devices, possessing the high sound velocity of diamond but requiring less materials processing.

The influence of varying nitrogen concentrations (5–1000 ppm) on the conventional CH 4 /H 2 diamond film deposition process using a microwave plasma disk reactor is investigated. This reactor has important differences, such as reactor volume, power density, gas flow, from the common tubular microwave reactors. The experimental behavior indicates, that similar to the tubular reactors, the addition of small amounts of a nitrogen stabilizes the growth of high quality, {100} faceted films. However, the actual threshold nitrogen concentrations and the variation of these threshold concentrations versus other independent experimental variables differs considerably from tubular reactor performance. This suggests that reactor design has an important influence on the deposition process in the presence of impurities.

Background To establish quicker cardiac arrest and less myocardial distension injury during heart procurement, we combined St. Thomas and histidine-tryptophan-ketoglutarate (HTK) solutions for donor heart preservation since June 2008. Methods From June 2008 to March 2010, we enrolled 31 heart transplantation (HT) patients in this study. During heart procurement we initially infused 1,000 mL cold St Thomas cardioplegic solution to achieve cardiac arrest. After procurement, a further 2,000 mL of cold HTK solution was infused at low perfusion pressure. Another 1,000 mL cold HTK solution was perfused before donor heart implantation. We examined donor age, recipient preoperative characteristics, ischemia time, hospital stay, postoperative graft function, major cardiac events, and transplant vasculopathy (TCAD). Results Twenty-two patients (71.0%) presented with dilated cardiomyopathy and 7 (23.3%) with ischemia cardiomyopathy. There were 23 (76.7%) male donors, and the mean donor age was 38.4 ± 13.8 years. Six patients underwent a redo sternotomy, 1 patient needed a third-do sternotomy, and 1 a seventh sternotomy (third HT) for repeated endocarditis and graft failure. The average ischemia time was 224.9 ± 71.0 minutes and the postoperative hospital stay was 57.7 ± 47.7 days. The surgical mortality (3.2%) was not accompanied by hospital or follow-up mortality. Patient left ventricular ejection fraction postoperative was 59.6 ± 2.3% with good functional status. Major cardiac events occurred in 8 patients (26.7%) without major complications. There were two subjects with TCAD but normal graft function. The correlation between ischemia time and hospital stay was insignificant ( r = 0.21; P = .26). Conclusions Donor heart preservation combining St Thomas cardioplegic arest and low-pressure perfusion with HTK solution seemed to be safe with. short-term survival similar to other approaches.

Optical absorption has been used to study polyaniline at various levels of oxidation and protonation. The conversion of leucoemeraldine base to its salt accounts for the blue shift of the π-π∗ absorption from 3.94 to 4.17 eV. The emeraldine base has an absorption peak at 2.1 eV due to the localized benzenoid HOMO (highest occupied molecular orbital) to quinoid LUMO (lowest unoccupied molecular orbital) excitation. Protonation of the emeraldine base causes a lattice distortion of polyaniline to form a polaronic lattice structure, which accounts for the shift of the 2.1 eV absorption to 1.5 eV. Further protonation of emeraldine salt causes the breakdown of the polaronic lattice to a confined bipolaron lattice. When the acid strength of the solution is very high (96% H2SO4), most of the amine nitrogens are protonated. Characteristic absorptions of isolated quinoid imine units (∼2.5 eV) and benzene units (∼4.8 eV) have been found. The evolution of band structure corresponding to the optical-absorption change during the protonation of polyaniline at each specific oxidation state is studied by gradually changing the acid strength of the solution to which the polymer is subjected. We have also studied the optical-absorption change at one fixed acid strength by slowly oxidizing leucoemeraldine to emeraldine then to pernigraniline by electrochemical and chemical means. Detailed information has been obtained on the band structure changes in relation to lattice structure interconversions during the transitions between various oxidation and protonation states.

A high performance 22/20nm CMOS bulk FinFET achieves the best in-class N/P I on values of 1200/1100 µA/µm for I off =100nA/µm at 1V. Excellent device electrostatic control is demonstrated for gate length (L gate ) down to 20nm. Dual-Epitaxy and multiple stressors are essential to boost the device performance. Dual workfunction (WF) with an advanced High-K/Metal gate (HK/MG) stack is deployed in an integration-friendly CMOS process flow. This dual-WF approach provides excellent V th roll-off immunity in the short-channel regime that allows properly positioning the long-channel device V th . Enhanced 193nm immersion lithography has enabled the stringent requirements of the 22/20nm ground rules. Reliability of our advanced HK/MG stack is promising. Excellent SRAM static noise margin at 0.45V is reported.

A dual-lateral well was completed in a Chevron subsea condensate field with high peak rate. Within one year, the production significantly declined with high water-cut. The well was shut down and then brought back to production, observing much reduced flow rate for three days and eventually stopped flow.

Summary form only given. It has been shown that even small concentrations of nitrogen have a substantial effect on the growth of CVD diamond films, while larger concentrations may result in degraded and rough growth. In the present study we show the effect of nitrogen concentration on the growth, texture, morphology, and crystalline quality of CVD diamond films. All films are heteroepitaxially grown on a 3 inch silicon substrate and are scratch-seeded with a seeding density of 10/sup 9//cm/sup 2/. A computer controlled 5 inch discharge 2.45GHz microwave plasma reactor with ultra-high vacuum gas handling systems combined with optical emission spectroscopy allows exact control of the gas phase concentrations and reactor input variables. Nitrogen gas phase concentration is varied from l0ppm to over 1000ppm and is controlled by the measurement of CN bands in the optical emission spectrum of the plasma. Pressure ranges from 38-50 Torr, methane/hydrogen from 0.5-2%, and flow rate from 50-200 sccm. Growth and morphology are carefully determined using SEM while texture is obtained using XRD. Crystalline quality is measured by determining the FWHM of the diamond Raman peak at 1332/cm using unpolarized micro-Raman spectroscopy. Detailed growth, texture, morphology, and crystalline quality maps are given to show the sequential effect of increasing nitrogen versus all other reactor input variables.

Summary form only given. Presently, plasma assisted synthesis of diamond films often employs a microwave discharge/reactor for the source of the radical species. Typical deposition takes place using varying CH/sub 4//H/sub 2//CO/sub n/ gas mixtures over a 20-100 Torr pressure regime and with a CW, 2.45 GHz input power of less than 3 kW. While excellent diamond films are synthesized under these conditions, the linear deposition rates are usually limited to only a few /spl mu/m/hr. Since diamond synthesis costs are still high, it is desirable to deposit high quality diamond films with higher deposition rates. One method to increase the diamond deposition rate is to increase the deposition pressure and discharge absorbed power density. This paper will present the results of an experimental investigation exploring microwave plasma synthesis at the 100-200 Torr pressure and 2.5-6 kW input power regimes. This work, which builds upon earlier reported work (Kuo et al., 1992, Kahler, 1997), utilizes a microwave reactor developed for operation at higher pressure/power regimes.

Summary form only given. Recent studies within our group have focused on the effects of nitrogen on diamond film growth. Very small concentrations of nitrogen have been shown to enhance CVD diamond film growth, while larger concentrations may result in rough growth. In any CVD growth, within several gas phase mean free paths of the surface, the composition of the gas is perturbed by the effects of the reactions occurring at the surface. A chemical boundary layer with temperature and concentration gradients is formed, through which species diffuse to reach the surface. Boundary layer transport in CVD diamond film growth has been studied for hydrogen, carbon and oxygen species. The transport of nitrogen has been less studied. Also the transport mechanisms and growth are somewhat specific to deposition conditions. Our deposition conditions are based on use of a five inch discharge 2.45 GHz microwave plasma reactor, and transport over wide areas has also been less studied.

Summary form only given, as follows. Argon-methane and argon-methane-hydrogen discharges used in a microwave CVD system for the deposition of diamond films are investigated in this study. These discharges have been used to produce small grain size diamond films, also known has ultra-nanocrystalline diamond. To further understand the plasma deposition process experimental measurements of the discharges have been undertaken. Specifically, the objective of this study is to determine the relationship of the deposition results versus plasma species concentrations and temperatures. The deposition discharges being studied are at pressures of 80-160 Torr with 0-3% methane and 0-10% hydrogen in an argon discharge. The plasma discharges studied are excited using a 17.8 cm diameter microwave resonant cavity reactor. The discharges are excited using 2.45 GHz microwave power in a discharge chamber with 12.5 cm diameter. Experimental characterizations include OES measurements of selected atomic hydrogen, C/sub 2/, and CH emission lines, and OES measurements of gas temperature in the discharge. Changes in the input gas composition are observed to produce substantial variations in these OES measurements. The measurements are conducted as functions of the discharge's quartz wall temperature (100-200 C) and the substrate temperature (400-900 C). The discharge experimental measurement results are also correlated with the properties of the diamond films deposited.

In a previous study we observed increased serum levels of a 3,3'-diiodothyronine sulfate (T2S)-like material (compound W) in women who received human chorionic gonadotropin (hCG) treatment. In the present study we assessed serum compound W values in 113 women (total serum sample: 190) with trophoblastic disease, in 7 normal nonpregnant women during the menstrual cycle and 7 women given hCG treatment in the course of in vitro fertilization. Fifty-three women with trophoblastic disease had serum free thyroxine (FT4) concentrations greater than 3.0 ng/dL with suppressed serum thyrotropin (TSH) levels; 61 had FT4 values less than 3.0 ng/dL with a mean TSH of 0.83 mU/L. Mean (+/- SE) compound W concentrations in the high FT4 group were significantly higher than in the low FT4 group (76 +/- 8.1 vs. 21 +/- 1.7 ng T2S equivalent, p0.001) There were significant correlations between serum hCG and compound W concentrations (r = 0.472, p0.001), serum FT4 and hCG (r = 0.503, p0.0001) and serum FT4 and compound W (r = 0.585, p0.0001). In nonpregnant women serum compound W levels increased from 7.5 +/- 8 ng/dL at the end of the menstrual period to 15 +/- 1.7 ng/dL 21 days after the last menstrual period. Finally, a single dose of hCG (10,000 USP units, intramuscularly) increased mean (+/- SE) serum compound W levels from 12.8 +/- 2.3 to 64 +/- 9.7 ng/dL and 54 +/- 12 ng/dL at 9 and 16 days, respectively. These results indicate that hCG and perhaps luteinizing hormone (LH) increase serum compound W concentrations in women. The mechanism and significance presently are unclear.

Abstract Texaco Canada Petroleum Inc., (TCPI) has successfully conducted a 10-horizontal well primary production pilot project at Frog Lake, Alberta, Canada, where the heavy oil gravity ranges from 10 to 14 API, and the oil viscosity ranges from 20,000 to 50,000 cp. These 10 wells were completed in the Lower Waseca formation (one of five prospective formations in the field) and produced using the primary production technique of "cold production", which is the coproduction of sand and oil from the reservoir at ambient temperatures. These wells were very successful with most wells displaying productive capabilities in excess of 100 barrels of oil per day. Based on the success of the 10-well pilot, a long term staged development plan was established that will allow resolution of some technical challenges also identified by the 10-well project. This paper summarizes "cold production" technology, the history of the Frog Lake field, completion and production techniques, and some of the operational and technical challenges encountered. A field wide development strategy and enhanced oil recovery potential are also discussed. Cold Production Technology A number of heavy oil and oil sand reservoirs in Alberta, Canada have been successfully produced under primary production at rates far in excess of the predictions based on radial Darcy flow. The primary heavy oil production is possible by allowing formation sand to be produced along with reservoir fluids using a progressive cavity (PC) pump. This process is called "cold" production because heat, such as steam, is not introduced into the reservoir to effect production of the heavy oil. Figure 1 shows a PC pump which can carry reservoir fluids and sand to surface through the rotational action of a rotor housed in a flexible rubber stator. Typically, a cold production well will produce oil and water at sand cuts as high as 30 to 40% initially, which gradually decrease over time to stabilize at between 1 to 5% after one year of production. Cold production technology has been applied to many heavy oil and oil sand reservoirs in the Cold Lake region of Alberta, Canada with economic success. Figure 2 shows a representative cold production project with a six year production history. The range of reservoir characteristics and fluid properties amenable to cold production are shown in Table 1. Currently, the two generally accepted theories on the dynamics of cold production are:sand production creates "wormholes" in the reservoir thereby increasing both the effective permeability and well bore radius, and;the oil flows due to the "foamy oil" phenomena, a type of reservoir drive mechanism involving the retention of solution gas by the viscous oil. Other factors contributing to cold production may include increased drainage radius, gas expansion, and continuous pore de-blocking. Higher quality PC pumps allow co-production of the sand with the heavy oil. Sand production is encouraged through large diameter perforations in vertical wells and wide slots in horizontal well liners. Anticipated recoveries are increased to 8 to 12% of the original oil in place from negligible levels if the wells were produced without the co-production of the sand. As horizontal well technology developed, demonstrated increases in oil production from three to four times that of conventional vertical wells were common. Although the cold production mechanism is not fully understood, a combination of horizontal wells and cold production does have the potential to economically produce many heavy oil fields. History of Frog Lake Property Texaco Canada Petroleum Inc. (TCPI) is a 100% working interest owner of a 34,000 acre 53 section oil sand lease located at Frog Lake, Alberta. P. 279^

Abstract In 1991, two horizontal wells were drilled in the Pittsburg "C" sandstone reservoir of the New Hope Shallow Unit (NHSU) in East Texas. The first well was a 457 m (1,500 ft) horizontal oil well and the second was a 457 m (1,500 ft) water injection well. The NHSU Pittsburg formation is a relatively tight sandstone reservoir undergoing a waterflood project expansion. It has a 45-year production history and is located at a depth of about 2,438 m (8,000 ft.). Different scenarios were examined by a simulation study to determine the optimum development program. The horizontal wells were drilled in the last quarter of 1991. This paper summarizes the engineering evaluation as well as the planning, drilling and completion of these wells. Production histories, as well as problems and their solutions to date, are also discussed. The project was a success in terms of the horizontal producer which tracks slightly below anticipated production. The horizontal injector was drilled in a tight zone which prevented water from being injected continuously into the formation. However, due to the success of the producer, it is shown that horizontal wells in sandstone reservoirs have potential of breathing new life into a tight waterflooded reservoir. Introduction Initially the horizontal well gained its fame in the mid-1980's for its application in the Austin Chalk formation for penetrating naturally fractured carbonate formations. As the industry is discovering, the horizontal well has many more applications, such as for thin formations, water or gas coning, viscous oil and EOR, low permeability gas reservoirs, and unusual gas sources such as coalbed methane or Devonian shale. The advance in horizontal well drilling techniques in recent years has allowed the horizontal well to become a less risky proposition. Its application in improving oil field recovery efficiency has just begun. The New Hope Shallow Unit is located in the New Hope Field, Franklin County, Texas. It is in the north central part of the East Texas Basin, some 32 km (20 miles) south of the Sulphur BluffTalco fault zone. Figure 1 is the location map of the New Hope Shallow Unit with the west side of the unit circled. Total area of the NHSU is approximately 2,065 ha (5,113 acres). The field was discovered in 1943 and a line drive waterflood was developed from east to west after the reservoir pressure was depleted. While the east side was nearly 100% waterflooded after 45 years of production, the waterflood on the west side was not fully developed. Before the horizontal wells were drilled, the west end Pittsburg reservoir was under a waterflood expansion with two water injectors and six oil wells which produced approximately 40 M3/day (250 BOPD). The average thickness of this reservoir is about 6.1 m (20 ft.) and it is a relatively tight (low permeability) formation. A long horizontal producing wellbore can greatly improve the productivity in tight, thin reservoirs and also reduce the cost of drilling many more vertical wells for achieving the same production rate.

Abstract In November 1992, a 2000-ft horizontal well was drilled in the Chuchupa Field, offshore Colombia. Chuchupa is a major gas field in Colombia, contributing about 90% of the gas supply for electricity generation on the northern coast of Colombia. This paper documents the selection, planning, reservoir simulation, drilling, completion and operation phases of this project. The horizontal well, Chuchupa 14, was successfully drilled from an offshore platform in 200 ft of water with a total horizontal displacement of 2000 ft. The entry point of the horizontal well is 6300 ft away from the platform. The formation is a semi-consolidated Chuchupa sandstone at a depth of 5325 ft sub sea, with average thickness of 167 ft, and average permeability of 209 md. Initial production test indicated that the well could be produced at 60 MMSCF/day on a 44/64" choke. This production rate is 4 to 6 times that of a conventional vertical well. Currently, the well is being produced from 40 to 60 MMSCF/day. In this application, the horizontal well can replace at least four vertical wells. With the development of horizontal wells, a significant amount of savings can be realized with fewer platforms and wells needed to develop the remainder of the field. INTRODUCTION The natural gas in the northern coast of Colombia is primarily supplied by two gas fields jointly operated by the Texas Petroleum Company and Ecopetrol. The Ballena Gas Field and the Chuchupa Gas Field in the Guajira area, shown in Figure 1, provided more than 90% of the gas supply for electricity generation in the coastal area. While the Ballena Field is partially onshore, the Chuchupa Field is about 7 miles offshore. The original gas in place for Ballena and Chuchupa are 1.5 and 4.2 TCF, respectively. Gas recovery in both fields is 30% and less than 30%, for Ballena and Chuchupa, respectively. According to a previous reservoir simulation study, some of the existing wells in the Chuchupa Field may face water breakthrough in a near future, therefore replacement wells are needed to insure a continuous supply of gas from this field. Horizontal wells are one of the option to be considered. BACKGROUND Figure 2 shows the isopach map of the Chuchupa Field with its discovery well Chuchupa 1 near the center of the field and the 8 vertical producers drilled from the platform. When the field was first placed on production in October 1979, the rate was at about 100 MMSCF/day. As of December 1991, 450 BCF of gas had been produced from the field with the average production rate of 104 MMSCF/day or 13 MMSCF/day/well for the 12 year period. Before the horizontal well was drilled, production from the eight vertical wells was 140 MMSCF/day.

Calorimetric measurements were made on a coprecipitation-synthesized GdBa 2 Cu 4 O 8 at temperatures between 0.5 and 13 K and in magnetic fields up to 7 T. The heat capacity data in zero field show an antiferromagnetic transition with T N ⋟ 2.2 K followed by a broad should below, which is identified from entropy consideration to be also associated with the Gd 3+ -ordering. Similar observations were made in a magnetic field of 2 T, except that T N was lowered to 1.6 K. At a higher field of 4 T the calorimetric signature of a long range ordering disappeared, leaving behind a Schottky-type anomaly with a peak near 1 K. This peak moved to 2.5 K at 7 T.

Summary Steamflood operations commonly encounter steam override problems. Close well spacing is one method used to reduce this effect. Blind spot areas still exist in the pattern, however, and leave substantial amounts of unrecovered oil after project termination. This study examines the effect of horizontal wells on improving steamflood conformance. A three-dimensional (3D) numerical steamflood simulator was used. The study involves the use of horizontal wells for mature steamfloods to reduce steam override that has already occurred and for prevention of steam override if used at the start of steamflood operations. The data used are from a typical California heavy-oil reservoir. Simulation indicates that horizontal wells can be effective for reducing or preventing steam override. For a mature 18.5-acre [7.5-ha] pattern, simulated horizontal wells increased ultimate recovery at the end of 11 years from 63.2 to 74.7% of original oil in place (OOIP). When used at the start of steamflood, a pattern of vertical and horizontal wells had a predicted recovery of 72.2% OOIP after only 7 years.

A commercial reservoir simulator capable of simulating operational changes in a steam flood was used to investigate the effect of steam slug size, water injection temperature, water injection rate and pattern lifting capacity in converting from steam to water injection. Inverted seven-spot and five-spot patterns were used for heavy oils and light oils reservoirs, respectively. The optimum steam slug size which is dependent on the injection, production and reservoir parameters was determined for both the heavy and light oil reservoir cases based on economic studies for realizing the maximum revenue on a project.