bluuebunny/crossref_metadata_2025_split huggingface dataset:
Commingled Production Wells: Experiences in Lake Maracaibo, Venezuela
Authors: Ferrer Fernando J. 
Published: December 2007

Abstract
For many years, commingled production has not been considered as a valid alternative to produce marginal fields. In fact, oil regulations in many countries do not allow this technique because it could affect the final recovery.
Venezuela is no exception to this practice, however some new technologies are arising to change this situation and make commingled production a valid alternative to improve the performance of marginal fields.
Most reservoirs in Block I Lake Maracaibo are already very depleted, so a plan has been designed to recover and increase remaining reserves. Among some other technologies such as slim hole and infill drilling, commingled production plays a key role in reservoir rejuvenation plans.
In this paper the basic fundamentals of this practice are discussed, showing a new methodology to estimate composite IPR curves, procedures and techniques used to quantify contribution from individual zones and criteria to select suitable well candidates for this purpose. Some results of a pilot test carried out in Block I Lake Maracaibo area are presented in order to show the benefits of commingled production.
P. 801
Alternatives to Monte-Carlo Simulation for Probabilistic Reserves Estimation and Production Forecasting
Authors: Mishra Srikanta 
Published: December 2007

Abstract
This paper describes three alternatives to Monte-Carlo simulation: (a) the first-order second moment method, (b) the point estimate method, and (c) the first-order reliability method, for the assessment of uncertainty in reservoir engineering calculations. These techniques are proposed as more suitable than Monte-Carlo simulation when information regarding parameter uncertainty is limited, the forward model is computation intensive, and/or the probability associated with only a limited number of model outcomes is of interest.
Method for Handling the Complexities Associated with History Matching the Performance of a Highly Stress-Sensitive Formation
Authors: Yang Zhengming , Ershaghi Iraj , Mondragon Julius J. , Hara Scott 
Published: December 2007

Abstract
This paper presents aspects of formation stress sensitivity influencing the successful simulation of the Tar Zone in Fault Block IIA of the Wilmington Oil Field in Los Angeles County, CA, USA. The Tar Zone is a slope and basin clastic type reservoir. The significant compaction experienced during the primary phase and the subsequent rebound during the following waterflooding created a complex case of reservoir definition for projection purposes. Uncertainties regarding stress effects on physical properties such as porosity, permeability, compressibility and formation thickness complicated the representation. The history matching attempts revealed the insufficiency of using conventional compaction models in the appropriate modeling of the compaction-rebound process. A new compaction-rebound feature was developed based on rock mechanics considerations and was incorporated into a commercial simulator, Computer Modelling Group's STARS™ simulator. This method allows for meticulous representation of the spatial dynamics of compaction/rebound based on the local pressure field.
A successful history match of the primary and waterflooding production was achieved with the new compaction/rebound algorithm. The model was successfully tested by predicting the 20 acre steamflooding pilot. The case under consideration is unique and relates to high pressure and temperature steamflooding. The proposed methodologies have widespread application in other stress-sensitive heavy oil reservoirs.
Effect of Brine Salinity and Crude Oil Properties on Relative Permeabilities and Residual Saturations
Authors: Filoco Paulo R. , Sharma Mukul M. 
Published: December 2007

Abstract
Centrifuge experiments were conducted on Berea cores to measure the drainage and imbibition relative permeabilities in two phase and three phase systems. Two crude oils, Prudhoe Bay and Shell Mars crude were used in our tests. No effect on oil recovery was obtained in the drainage experiments when the crude oil was displaced by air at connate water. However in the imbibition experiments the oil recovery increased significantly with the salinity of the connate brine. The salinity of the displacing brine had no significant influence on the oil recovery. The relative permeability curves obtained during drainage were also found to be insensitive to the salinity of the brine. However the imbibition relative permeability curves show a strong salinity dependence. A comparison of the two crude oils and a nonpolar mineral oil indicates that the more water-wetting Mars crude oil shows a higher oil relative permeability at the same bond number compared to the mixed-wetting Prudhoe Bay crude oil. The salinity dependence of the residual saturations and the relative permeabilities clearly indicate that the change in wetting properties of the rocks surfaces from water-wet to mixed-wet during the drainage process is an important factor controlling the imbibition relative permeability curves. This clearly suggests that the performance of waterfloods will be strongly affected by the composition of the crude oil and its ability to wet the rock surfaces, the salinity of the connate brine in the reservoir, and the height above the o/w contact.
Fracture/Stylolite Characterization Using Stochastic Modeling in Zone-II Reservoir, Offshore Abu Dhabi
Authors: Bushara M. N. , Arab H. M. 
Published: December 2007

Abstract
This work evaluates effects of open fractures and sty lolite networks on total permeability of Zone-ll reservoir system. Database is compiled from detailed analysis of cores, dipmeter and FMS/FMI images. Geostatistical 3D stochastic models were built for 23 cored wells containing matrix permeability, fracture and stylolite densities, along with empirically computed maximum principal strain (εmax) from fractures. The magnitudes of strain tensor are taken to be proportional to the aperture of fractures in a direction predicator to their orientation. Comparison of upscaled average surfaces of these data with test permeability values suggests that there is a genuine permeability contribution from fractures in the reservoir. A technique is developed to transform matrix permeability realizations so as to honor test permeability, predict fracture permeability fieldwide, and better account for water breakthrough trends.
Effect of Dolomitization on Relative Permeability and Its Interpretation by Network Model
Authors: Namba Takao , Ishibashi Masatoshi , Tanaka Hiroki 
Published: December 2007

Abstract
Core and log data review for an Upper Jurassic carbonate reservoir in Middle East indicated that log derived dolomite content has correlation with relative permeability data. This result motivated further petrographical and mineralogical analyses, which revealed that dolomitization occurred in two stages. The dolomitization during the early stage displaced original grains by dolomite, and the further dolomitization displaced calcite cement (isopachous fringing cement) by rhombic dolomite crystals, which homogenize pore-throat system.
Pore network model was utilized to understand the observations, highlighting the gas-oil system in this paper to avoid wettability uncertainty problems which is inherent in oil-water system on carbonate rocks. The drainage gas oil relative permeability data of a high dolomite content sample (dolostone) with a well sorted pore-throat system was successfully duplicated by the pore network model. Although quantitative interpretation was not achieved for a dolomitic limestone sample with a complicated pore-throat system, the trend of gas relative permeability change due to the homogenization and enlargement of pore-throat system by dolomitization, which was modeled by Weibull function, was reproduced by the network model.
Reservoir Simulation Optimises the Development of the Yibal Field
Authors: Cook R. C. H. , Lozano J. A. 
Published: December 2007

Abstract
This paper presents the ongoing development, by horizontal drilling, of the giant Yibal Field, Oman. In particular, the paper discusses the substantial improvement in new well performance as a consequence of comprehensive reservoir simulation modeling.
Yibal field development consists primarily of drilling new horizontal sidetrack producers from watered-out vertical wells. Two rigs are occupied full time in Yibal drilling, on average, 38 horizontal sidetracks per year. During 1997, a portfolio of eleven dual porosity simulation sector models was built covering more than 90% of the Yibal Field. New wells are now directed at the remaining oil targets imaged by these simulation models. Some 70 of these ‘smart’ wells have now been drilled. The running average initial net oil rate is 950 m3/d which represents a 12% improvement versus the 1996 wells. The watercut trend has improved even more and now averages just 21% versus 41% for the 1996 wells. This is particularly important as field production is now nearing its gross capacity constraint. As a result of simulation modeling and the drilling of ‘smart’ wells, Yibal Field production is now 35×103 m3/d which represents an all time high after thirty years of field production history.
To ensure that the current gains are not lost, work has already begun upon a new portfolio of fine grid simulation models. It is anticipated that the increased model resolution will image the smaller oil targets which will be pursued in future as well spacing shrinks under continuous infill drilling. Much of this future drilling will involve novel techniques such as slimhole sidetracks, underbalanced coiled tubing slimhole sidetracks and multilateral drilling, both conventional and slimhole. A number of these techniques are currently being trialed at Yibal.
Real-Time Artificial Lift Optimization
Authors: der Kinderen W. J. G. J. , Dunham C. L. , Poulisse H. N. J. 
Published: December 2007

Abstract
Shell has introduced a computer infrastructure for on-line, real-time production optimization. Several years of experience have been captured in a range of application packages, from well test management to optimization software for gas-lift, electrical submersible pumping, beam pumping, and injection systems.
Recent developments include a well test optimization algorithm (called WellDone) that analyses test-separator measurements in real time. Another area of innovation is online, multi-phase production measurement using simple, readily-available instrumentation. Field tests confirm that the liquid production of a well can be estimated and trended from the pressure drop across an (existing) flow line restriction. This DeltaP method can be used for enhanced well test scheduling, and for continuous measurement of the incremental gas utilisation factor (IGUF), i.e. the response of a gas-lift well to changes in lift gas injection rate. In another new development, gas-lift wells which exhibit unstable behaviour can be stabilised by active control of the production choke. The potential benefits of this novel DynaCon technique have been demonstrated in the laboratory and a field trial is on-going.
Regional Basin Modelling: An Approach to understand Shelfal Carbonate Reservoirs of the Oxfordian and Kimmeridgian in Offshore Abu Dhabi
Authors: Al-Suwaidi A. S. , Aziz S. K. 
Published: December 2007

Abstract
Exploration activities in Abu Dhabi have traditionally been focused on the reservoir zones of the lower Cretaceous Thamama Group and the Jurassic Arab and Araej Formations. The carbonate reservoirs developed along the eastern flank of the Oxfordian - Kimmeridgian intra-shelf depression in offshore Abu Dhabi received less attention, until recently when commercial oil accumulations in structural traps were discovered. A multidisciplinary study using sequence stratigraphic approach resulted in clarifying the geometry and the chronostratigraphic relationships of the identified sequences. The study included regional seismic data, litho-biofacies studies, geochemical analysis, strontium isotope age dating and well logs from over 50 wells.
After the deposition of the Callovian Upper Araej member, a differentiated carbonate platform was initiated in early Oxfordian in offshore and western onshore Abu Dhabi where tectonic subsidence coupled with sea level fluctuation controlled the geometry, deposition and the distribution of variable lithofacies that ranged from organic rich limemudstones in the depressed area to porous and permeable bioclastic packstones. grainstones and dolomites in the shallow waters along the eastern flank of the intra-shelf basin.
Detailed study resulted in identifying four 3rd-order sequences in the Oxfordian to Middle Kimmeridgian stages in the offshore area. Sequence-1 is entirely Oxfordian and is deposited during transgressive and highstand periods dominated by aggrading and prograding geometries. Sequence II is Lower Kimmeridgian and represented by a well-defined lowstand system tract followed by short-lived transgressive and highstand system tracts. Sequence III is mainly deposited during a lowstand period capped with a shelf margin wedge system tract. Finally, Sequence IV was deposited entirely during transgressive and highstand periods on an undifferentiated platform with minor depression in the western area. Two type I sequence boundaries have been interpreted at the top of Sequences I and II in the shelfal area. The best reservoir developments occur in the bioclastic packstone and grainstone facies deposited during the highstand periods below the Sequences I and II boundaries where the reservoir units are characterized by porosities of &lt; 20% but with very high permeabilities reaching a few Darcys. The basinal facies of Sequence I exhibits the best source potential in the intra-shelf basin, whereas the remaining sequences show marginal source rock richness.
Distribution and Origin of a Tar mat in the S. Field (Abu Dhabi, U.A.E.)
Authors: Carpentier B. , Hue A.-Y. , Marquis F. , Badr A. E. R. , Al Aidarous A. A. , Al-Baker S. 
Published: December 2007

Abstract
This study has been conducted to investigate the distribution and origin of bitumen (tar mat) occurring in the Thamarna Zone B reservoir (Upper Kharaib Fm., Lower Cretaceous) of the S. Field in Abu Dhabi.
The main objective was to assess the continuity of the bitumen rich interval and its possible role as an intra-reservoir permeability barrier potentially responsible for the pressure anomalies recognized at the field scale during oil production.
Detection of bitumen was performed on 68 wells using petrophysical data, Rock-Eval and electrical-log derived methods. The result provides a realistic 3D image of the tar mat distribution at the field scale.
Biomarker analysis suggests that there is no difference in origin nor maturity between the tar mat and the overlying oil. Comparison between bitumen location, sedimentological facies, petrophysical properties, field structural history, present-day and paleo-OWCs were used to decipher the process and timing of the tar mat deposition.

Results, Observations and Conclusions
A tar mat (4 to 23 ft thick) is present in the crestal part of the field and is located at the base of Thamarna Zone B, increasing the role of vertical permeability barrier formed by the underlying "Dense Limestone". The bitumen is clearly associated with the low porosity zone located at the base of the Thamarna B and seems to be never present in the water leg nor related to the present day or paleo-OWCs. The formation of the tar mat is probably post-Dammam (Eocene) in age and is likely to be due to flowing down of a gravity segregated heavy fluid which is eventually trapped in the low porosity base of the reservoir.

Applications
The results demonstrate that the bitumen rich interval is not responsible for the pressure drop during production and will not play the role of permeability barrier between the central and northern part of the field where gas injection is planned. The provided 3 D distribution of the bitumen volume allows a better estimate of the OIP (oil in place).

Technical Contributions
Feasibility Study for Seismic Monitoring of Gas Injection
Authors: Nishida Akio , Ito Toru , Suzuki Koichi , Sato Makoto , Shimada Nobusuke 
Published: December 2007

Abstract
In this study, seismic monitoring of injected gas in a carbonate reservoir was investigated using multidisciplinary approach which consisted of geological/reservoir modeling, reservoir flow simulation, rock physics and seismic modeling. A case-study was conducted over the Lower Cretaceous carbonate reservoir offshore Abu Dhabi.
The gas saturation and reservoir pressure data were obtained from the reservoir flow simulation. The velocity data of dry rock samples under the various conditions were also obtained from rock physics study. These outputs were converted to the velocity model using Gassmann 's equation. The calculated velocity from Gassmann's equation is well correlated with velocity from laboratory measurements. Therefore we can confirm that the Gassmann's equation is applicable to estimate the velocity of the gas saturated reservoir rock.
Based on the velocity model, synthetic seismic sections before and after gas injection were constructed in order to verify the influence of gas flood. As the results, amplitude difference between the two synthetic seismograms was observed at top and bottom reflectors of the reservoir zone. This amplitude variation is caused by both gas saturation change and pressure change. Although further investigation is needed to detect the cause of the variation, this study indicates the possibility of seismic reservoir monitoring
The Successful Redevelopment Of Existing Wells Using Multilateral Drilling Techniques
Authors: Tantawi Ibrahim , Taylor Randolph , Russell Rick 
Published: December 2007

Abstract
In the Zakum field multilayered carbonate reservoirs are separated by hard, impermeable layers. The field was developed during the past 20 years with conventional deviated (and, more recently, horizontal (wells, with openhole completions. Because production in certain older wells had begun to decline, various techniques to boost production were investigated. Trials showed that using multilateral drilling techniques to access the reservoir's individual layers offer a significant improvement in production rates. Subsequent drilling of several multilaterals substantiated the trials findings. The reservoirs' layered nature and the existing well designs required use of innovative directional drilling tools and techniques. Case histories demonstrate the techniques used and the resulting improvements in production.
Several multilateral re-entry wells with as many as six horizontal branches have been drilled into this article's subject reservoir. Lateral sections as long as 2,500 ft have been achieved, often including turns of up to 180 (to optimise production rates. Sidetracking out of existing casing and from open hole has been required with build rates exceeding 60(/100 ft. A unique non-articulated drilling motor and measurement-while-drilling system has been used with very successful results. Production rates from the multilaterals have improved significantly. It can thus be concluded that the use of complex multilaterals provides an economically and technically viable solution to the reservoir's declining production.
Laboratory Studies of Gravity Drainage Mechanism in Fractured Carbonate Reservoir - Capillary Continuity
Authors: Sajadian V. A. , Danesh A. , Tehrani D. H. 
Published: December 2007

Abstract
In the well fractured carbonate reservoirs the gas/oil gravity drainage from the gas-invaded zone is the dominating oil producing process. When the gravitational forces exceed the capillary forces, the matrix blocks which are surrounded by gas, will release their oil.
The results of our experimental works reveal that, depending on the interfacial tension, spreading coefficient, rock wettability, and surface roughness, there is a critical fracture aperture size, tfc. When the fracture aperture is more than tfc, the continuity is via solid compressed spacers and/or oil film around them, which at actual reservoir conditions it may be considered as non-effective capillary continuity. Whereas for the case that the fracture aperture is less than its critical value, the capillary continuity is mainly through liquid bridges which due to their high transmissibility will result in an effective capillary continuity between blocks.
Two new definitions for horizontal fracture capillary pressure based on the type of capillary continuity have been presented. Laplace formula and pressure difference between the fracture gas and the matrix oil may be used for calculation of fracture capillary pressure for non-effective and effective continuity, respectively.
Experimental and Numerical Modeling of Sulfur Plugging in a Carbonate Oil Reservoir
Authors: Al-Awadhy F. , Kocabas I. , Abou-Kassem J. H. , Islam M. R. 
Published: December 2007

Abstract
Many oil and gas reservoirs in the United Arab Emirates produce large amounts of sour gas, mainly in the form of hydrogen sulfide. In addition to creating problems in the production line, wellbore damage is often reported due to the precipitation of elemental sulfur in the vicinity of the wellbore. While there have been several studies performed on the role of solid deposition in a gas reservoir. However, the possibility of sulfur deposit in oil reservoirs has not been investigated in the past.
This paper presents experimental results along with a comprehensive wellbore model that predicts sulfur precipitation as well as plugging. The experiments are conducted in a core (linear system). Both analytical and numerical modeling are performed in a linear coordinate system. Data for the numerical model are obtained from both test tube and coreflood experiments. By using a phenomenological model, the wellbore plugging was modeled with an excellent match (with experimental results).
The crude oil was de-asphalted prior to conducting the experiment in order to isolate the effect of asphaltene plugging. A series of coreflood tests was carried out to observe sulfur precipitation and plugging in a carbonate rock. Significant plugging was observed and was found to be dependent on flow rate and initial sulfur concentration. This information was used in the phenomenological model that can be incorporated in the wellbore numerical model.
External Corrosion of Gas Transmission Lines
Authors: Dos Santos Alfredo 
Published: December 2007

Abstract
This paper aims at highlighting the importance of decision making at design stage concerning materials selection and other measures for corrosion control and their relationship with environmental modes of pipeline degradation.
Two cases of gas transmission lines which experienced chloride stress corrosion cracking and corrosion under insulation are discussed to illustrate the shortcoming of selecting materials for internal corrosion control without regard to risks of external corrosion due to exposure to soil and atmospheric environments.
The paper concludes that knowledge and anticipation of all potential corrosion mechanisms at design stage are pre-requisites for long term pipeline availability and economic operation.
A Major Revamping Project with Minor Disruption to Operations
Authors: Coupaud Jean-François , Yahya Amer , Tailliart Jean-Marie 
Published: December 2007

Abstract
"An ageing oil field is like an old man: it must be handled very gently". To keep it alive, you may need major surgery, but it has to be done extremely carefully in order to avoid putting it into an irreversible state of shock. Our 25 year-old field was in desperate need of rejuvenation, by means of breathing support and complete overhaul of the nervous system; it also had to give up smoking.