bluuebunny/crossref_metadata_2025 huggingface dataset:
Horizontal Open Hole Well Displacement Practices: Effect of Various Techniques on Well Productivity, Operational Complexity, and Overall Project Economics
Authors: Mathis Stephen P. , McCarter Michael L. , Schottle Gary , Upchurch Eric R. , Gleason Mike
Published: December 2007

Open hole gravel pack completions can have many advantages over comparable cased hole completions. This is especially true for horizontal well applications. However, because no perforations are present to penetrate the filtercake, borehole conditioning prior to gravel packing is critical to ensure good well productivity. To address this issue various borehole cleanup techniques have been developed. These different techniques have been adopted to address specific reservoir and economic conditions. Various levels of success have been realized for these techniques, with their development leading to an improved understanding as to which steps are critical for success under any circumstance.

This paper reports performance results from gravel packed horizontal wells completed in the East Wilmington Field. In addition, techniques applied elsewhere are reviewed. The conditions that must be met in all displacement techniques to ensure a successful completion are outlined, as will the benefits and drawbacks of each of the commonly applied methods. Guidelines for selecting a wellbore cleaning procedure to employ in specific situations are provided.
Performance of Horizontal Wells in Gas Condensate Reservoirs, Djebel Bissa Field, Algeria
Authors: Dehane A. , Tiab D.
Published: December 2007

Properties of gas condensate reservoirs are particularly difficult to study due to the composition and phase changes of light components that occur during the reservoir depletion. At the first stage of their discovery, these reservoirs behave like gas reservoirs during depletion. Once the dew point pressure is reached at reservoir conditions of pressure and temperature a retrograde condensation phase develops in the reservoir. Liquid condensation in the formation can result in severe loss of well deliverability and therefore of gas and condensate recovery, which will certainly lead to a loss of income.

In this study, the performance of horizontal wells and vertical wells in Gas condensate reservoirs is investigated under various depletion schemes. The expected low horizontal well drawdown pressure, compared to vertical well for the same flow rate, considerably reduces retrograde condensation. A reservoir simulator is used to compare liquid saturation profiles in the case of horizontal and vertical wells in Gas condensate reservoirs. The influence of the horizontal well length section and reservoir thickness on horizontal well productivity, and condensate recovery were also simulated. Another factor investigated in this study is the effect of drilling a horizontal well in a Gas condensate reservoir that has already been developed by vertical wells.

To illustrate the productivity increase due to the use of horizontal wells in gas condensate reservoirs, Djebel Bissa field data are presented and discussed using a compositional single well model (VIP simulator). The main results of this investigation are:

Because pressure drawdown is smaller for a horizontal well than that for a vertical well, the problems related to the liquid deposit can be reduced by the use of horizontal wells. Layers of value of kh contains the most liquid accumulations.
Use of MASTER Web to Improve History Matching
Authors: Chang Shih-Hsien , Grigg Reid B. , Sung Andrew H.
Published: December 2007

History matching is a long-standing problem in reservoir simulation. Although automatic history matching is a difficult process due to the large number of variables and high degrees of uncertainty, it is possible to develop methodologies to improve the matching process. This paper presents MASTER Web, a software tool for configuring a web-based parallel computing system on a cluster of PCs to support a new approach for history matching. A simple, Java-based software has been implemented to connect/communicate heterogeneous (different hardware and operating system) PCs for carrying out the matching process. MASTER Web, a loosely coupled parallel system (with no shared memory) configured in a master-slaves fashion, is sufficient for history matching since there is no need for inter-slave-processor communication. Utilizing parallel computing across the network (the Web), this novel technique not only aims to improve history matching, but does it economically on clusters of ordinary PCs, making it affordable for smaller oil companies. There are a great number of applications of this technique in reservoir simulation. Every application that requires a large number of repeated simulation runs can be improved with MASTER Web. The results we obtained are highly encouraging and indicate the great potential of our approach. Our experiments, carried out with a small cluster of PCs, have achieved a significant practical speedup in terms of wall clock time.
Innovative Drilling Fluid Design and Rigorous Pre-Well Planning Enable Success in an Extreme HTHP Well
Authors: Oakley D. J. , Morton K. , Eunson A. , Gilmour A. , Pritchard D. , Valentine A.
Published: December 2007

Drilling in the Qiongdongnan Basin, offshore China's Hainan Island Province, has often resulted in failure to reach desired objectives. Bottomhole temperatures up to 475°F, and pressures requiring mud weights up to 19.5 lbm/gal equivalent, place severe limitations on the performance of drilling fluids and often contribute in failure to reach the desired drilling objectives.

Well Yacheng 21-1-4 was drilled in this basin with the COSDC semi-submersible rig Nanhai V and was spudded on 27th November 1998. TD of 5,250 meters was attained on 20th May 1999 where the bottomhole static temperature was 414°F and the pore pressure was 18.5 lbm/gal equivalent. Logs were run to bottom without incident with no significant drilling fluid related problems and the primary drilling objectives achieved. The success is attributed to innovative, fit-for-purpose drilling fluids and rigorous pre-well planning over a 2-year period prior to the well commencing.

The paper describes the holistic approach to drilling fluid engineering for extreme well conditions. The development of innovative drilling fluids specific to these well conditions, and the rigorous laboratory testing necessary to generate detailed engineering guidelines, are described. Large-scale abrasion and pressure tests were also conducted. Modifications made to the rig design facilitated the management of drilling fluid properties at high density with high flow line temperatures. A portable drilling fluids laboratory, staffed with trained technicians, was installed on the rig to continually pilot test drilling fluid samples and treatments under simulated down-hole conditions. The importance of good communications and global technical support networks proved invaluable during the pre-well planning and for the execution phase of extreme high temperature and high pressure wells drilling.
Successful Isolation of an Overpressured Gas Zone Using an Expandable Drilling Liner
Authors: Metcalfe Paul , Martyn Kevin , Aitken Scott
Published: December 2007

This paper describes how an expandable drilling liner was used to isolate an overpressured gas zone in a well at a depth of over 13700ft. The liner was deployed for a Venezuelan operator in an onshore field. The liner was run below 9-5/8" casing and expanded from 6-5/8" to 9-5/8" thereby retaining hole size and allowing the well to be drilled to TD without a change in the original casing design.

The paper describes the planning involved in preparing the programme and how several new techniques were developed to ensure success in the field. Described in this paper is the selection of under-reaming parameters, development of cement placement techniques for expandable liners, expandable liner burst and collapse calculations and new milling & dressing techniques.

The application of expandable drilling liners to operations in the Asia-Pacific region could be considerable. Several applications have been considered, including offshore Vietnam, Sarawak and offshore Australia. The aim of this paper is to educate the region on the recent improvements that have taken place in other areas.
New Additive for Improving Shearbond Strength in High Temperature and Pressure Cement
Authors: Rudi Rubiandini R. S.
Published: December 2007

The quality of oil well cement is very important in maximizing the rate of production from an oil well. Good bonding between cement and casing also between cement and rock formation are essential for effective zone isolation, hence usually the additive should be added in order to improve the characteristics of standard cement.

The purposes of this research are to find the effect of adding expanding material, burnt pure-MgO, on the value of compressive strength and shear bond strength of API class G in high pressure and high temperature condition.

The method that has been used in this research is evaluating data from simulator, which was set up similar to field condition, 100 – 200 °C and 2000 psi.

According to the research, some conclusion can be drawn: adding expanding additives, in fact, will increase shear bond strength but will reduce compressive strength although generally still higher than recommended minimum value. The Appearance of mud cake will decrease shear bond strength. For compositions without expanding additives, shear bond strength was dropped drastically. MgO shows excellent performance, as expanding additive, in increasing the shear bond strength.

For low conditioning temperature, 100 – 135 °C, MgO that are burnt at 1000 °C are reliable, whereas for higher conditioning temperature up to 200 °C, the pure MgO which are burnt at 1200 °C, are more convenient. The concentration of expanding additives, which could be used to increase the shearbond strength of cements, are around 5%.
Development of a Casing/Drilling System Improves the Drilling Process
Authors: Skinazi E. , Deady R. , Robson D. , Konschuh C.
Published: December 2007

Drilling technologies continue to be driven by — and developed in spite of — the fluctuations in the price of crude oil. In an effort to further optimize the drilling process, especially for deep-water exploration, a system has been developed that allows casing to be run during drilling of a well.

The Casing/Drilling System ("CDS") will save rig time by altering the traditional drilling process. This system has been designed primarily for multi-well offshore platforms, multiwell operations on land, deep-water operations, and for situations requiring operators to drill through and place casing across problem formations quickly. This technology uses a combination of traditional components — bits, mud motors, MWD/LWD tools — as well as some newly developed components that allow drilling of most hole sizes from any drilling unit, with the ability to recover the drilling assembly using wireline or drill pipe.

This paper will describe the physical components and operational aspects of the casing drilling system. Actual well data will demonstrate the value of the system and the lessons learned during initial field use.
NMR T1 and T2 Relaxation in Oil-Based Mud Filtrates at Reservoir Temperatures
Authors: Kumar Nitesh , Jacob James , Davis Lorne A.
Published: December 2007

Knowledge of the nuclear magnetic resonance (NMR) properties of the near-wellbore fluids at reservoir temperature is needed for planning and interpretation of an NMR logging program. If the oil-based mud filtrate (OBMF) is the nonwetting pore phase, it will exhibit long, bulk fluid-like relaxations that can strongly affect the NMR response of the flushed zone. Knowledge of the NMR T1 and T2 relaxations at reservoir temperature is needed, since these parameters have significant temperature dependences. In this work, the bulk-fluid NMR T1 and T2 responses of six oil-based mud filtrates and three drilling fluid base oil samples were measured over a range of elevated temperatures. The present work also has application to NMR lab measurements on core taken with low invasion oil-based coring fluids.

All samples were degassed using a standard helium sparging technique, since dissolved paramagnetic oxygen can greatly reduce the NMR relaxations of refined oil products. The experimental temperature range was approximately 30100 C (546-670 °R). The temperature dependence of the bulk viscosity of each sample was measured using a rolling ball viscometer. The NMR relaxation data was collected on a 2 MHz permanent magnet spectrometer.

There were no important NMR relaxation differences between base oils and their derived mud filtrates. Sample viscosity had an approximately linear inverse relationship with temperature. The sample relaxations varied approximately as the inverse cube power of viscosity, steeper than has been observed in dead crude oils. For all samples, T1 and T2 increased approximately linearly with temperature, tripling from 30 to 100 C (546-670 °R).
Integrated study of Vatyogan oil field, West-Siberian region of Russia
Authors: Sharma R. , Bondarev A. , Sharry J. , Shelepov V. , Greensmith M. , Gavura A. , Kataev O.
Published: December 2007

The western Siberian basin contains some of the largest oil fields in Russia and the former Soviet Union. In early 2000, LUKOil, in cooperation with PetroAlliance, completed the largest integrated reservoir study ever undertaken in the region. The project spanning nearly four years culminated in an enhanced 3D geological and reservoir models of the giant Vatyogan oil field, which holds over 1 billion tons of calculated oil reserves.

The major technical objective was to utilize state-of-the-art technology to create a new 3D geological model of Vatyogan’s six major producing zones, which range in age from Upper Jurassic to Upper Cretaceous and cover a wide range of depositional environments. The new geologic model would form the basis for reservoir simulation models which would guide further operational and development activities in the field. Specific tasks to be accomplished with the new model include: In undeveloped areas: Estimate reserves and prepare a drilling programIn developed areas: Identify areas of by-passed oil and develop an optimum infill drilling and enhanced recovery program to improve production.

A multi-disciplinary team of 25 specialists was involved in various stages of the project. The study began with the creation of a digital database of 3,800 wells from paper records. Newly acquired data such as: 2D and 3D seismic, log data, and high precision gyroscopic surveys were incorporated into the revised models.

This paper describes the processes employed in the project and highlights some of the stumbling blocks. Details are provided describing data management, geological modeling, upscaling and history matching of thousand of wells. Conclusions illustrate how data from the specialized logs and high precision gyroscopic surveys resolved numerous questions and contradictions in the existing data, providing improved reservoir structure analysis and more accurate fluid-contact depths--data which significantly impacted both the models and the simulation forecasts.
Aspects of Multicomponent Resistivity Data and Macroscopic Resistivity Anisotropy
Authors: Schöen J. H. , Yu Liming , Georgi D. T. , Fanini O.
Published: December 2007

New induction logging hardware makes it possible to obtain both resistivity and resistivity anisotropy data. Resistivity anisotropy, the ratio of vertical to horizontal resistivity is the macroscopic effect of thinly layered formations in which logging tools have insufficient vertical resolution to properly resolve the individual beds or laminae. Generally, there are two types of layering: Laminated shaly sands. The sediment consists of thin bedded sand-shale sequences (anisotropy in these sands originates from the contrast of shale and sand resistivity).Finely layered anisotropic sands. The sand is composed of layers of different grain sizes and/or sorting (anisotropy in these sands originates from the resistivity contrast associated with the different water saturation).

The interpretation of conventional resistivity data is well understood. However, interpretation of vertical resistivity and resistivity anisotropy is not well understood and often counterintuitive. We have used forward modeling to illustrate the effects of porosity variability in layered formations. For example, we have investigated the porosity layering effect, which varies from an average porosity of 20 p.u. by +/- 5, 10, 15 p.u.. Three types of layering were considered: graded bedding, square- and sin2-variation of porosity with depth. The modeling shows that sharp bed boundaries create the maximum resistivity anisotropy for any two component resistivity distributions.

The new induction logging hardware is comprised of three mutually orthogonal transmitter-receiver coil configurations measuring all necessary data to derive both resistivity and resistivity anisotropy of the formation in vertical, deviated, and horizontal wells. Simple models illustrate the physics and the tools' capabilities are demonstrated with a synthetic example. Based on the petrophysical analysis of porosity contrast and layering type, a resistivity model is constructed and the tool responses of this model are computed. Using state-of-the-art inversion techniques, both resistivity and resistivity anisotropy can be recovered.
Measurements and Simulation of Inertial and High Capillary Number Flow Phenomena in Gas-Condensate Relative Permeability
Authors: Mott Robert , Cable Andrew , Spearing Mike
Published: December 2007

The productivity of most gas condensate wells is reduced significantly by condensate banking when the bottom hole pressure falls below the dew point. The most important parameter for determining condensate well productivity is the effective gas permeability in the near well region, where very high velocities can occur. An understanding of the characteristics of high-velocity gas-condensate flow is necessary for accurate forecasts of well productivity.

A number of laboratory experiments have demonstrated that gas condensate relative permeabilities increase at high velocity, reducing the negative impact of condensate banking on well productivity. On the other hand, inertial (non-Darcy) flow effects can reduce the effective gas permeability and lead to lower productivity.

This paper presents results of relative permeability measurements on a low permeability sandstone core, using a 5-component gas-condensate fluid. The experiments used a pseudo-steady-state technique at high pressure and high velocity, measuring relative permeability under conditions similar to the near-well region of a gas-condensate reservoir.

By carrying out measurements at a range of interfacial tensions and velocities, the results can be used to distinguish between high capillary number and inertial flow effects, and to quantify the impact of these two conflicting phenomena. The experiments suggest that the inertial flow coefficient in a 3-phase gas-condensate-water system is about 50% higher then in the equivalent 2-phase gas-water system.

The results of these experiments have been modelled through a correlation of relative permeability versus capillary number, together with an inertial flow correction to the gas permeability. The paper discusses these models and demonstrates how they can be used to calculate gas-condensate well performance in full-field reservoir simulation.
Development of a Through-Flow-Line TFL-Deployed Insert Surface-Controlled Subsurface Safety Valve
Authors: Abou-Sayed Omar A. , Reeves Harold J. , Valencia Randy L. , Holcombe Gary D.
Published: December 2007

BP Amoco’s Pompano Phase II subsea development is located in the Gulf of Mexico in Block 28 of the Mississippi Canyon. The water depth is approximately 1,865 feet. The subsea template is tied back 4.5 miles to the Pompano platform located in Vioska Knoll Block 989. Phase II development is a 10-slot, integrated template/manifold.

When the tubing retrievable safety valve (TRSV) in the primary and secondary production bores in two of the subsea wells failed, the wells had to be shut-in. An innovative through-flowline (TFL)-deployed insert surface-controlled subsurface safety valve (ISCSSV) enabled BPAmoco to restore operability and integrity to these wells. Root cause analysis had determined that declining reservoir pressures leading to excessive control-line differential pressures compromised at least of at least one of the tubing retrievable safety valves run with the original completions in 6 of the 8 subsea wells. Several options for remediation were considered: Floating rig interventions at an estimated cost of $610MM per well, orCodevelopment with an oilfield engineering/service company of a TFL-deployed insert SCSSV.

The second option was chosen, and involved both design work, as well as a rigorous test program.

The development and installation of these inserts allowed production in two subsea shut-in wells to be restored. This operation was the first in the Gulf of Mexico in which a TRSV lockout and the insert of a 3-in. insert flapper safety valve was deployed. BP Amoco’s TFL requirements have led to significant enhancement of TFL technology in general, and the maturation of this project was able to provide BPAmoco with capability to realize a substantial saving in operating costs.
The Significance of Risk Definition on Portfolio Selection
Authors: McVean J. R.
Published: December 2007

Efficient frontier portfolio analysis considers the balance between value and risk in the selection of "optimal" portfolios. Efficient frontier theory was originally developed for the realm of securities portfolios, where considering risk and uncertainty as synonymous may be appropriate. However, the appropriateness of this assumption has come to be questioned for petroleum portfolios. By examining the possible portfolios made up of a subset of 30 fictional but realistic projects, the significance of the definition of risk is explored. For each project, several risk profiles were generated based on different measures of value using Monte Carlo simulations. The definitions of risk that are explored include the standard deviation of the portfolio’s risk profile, the semi-standard deviation of the risk profile, the tenth percentile of the risk profile, and the probability of the measure of value being less than a specified threshold. The impact of risk being based on measures of value other than that used as the principal value measure is also explored. The conclusion is that the selection of an "optimal" portfolio is strongly dependent on which definition of risk is selected. Consequently, it is important to explore multiple risk definitions in order to more fully understand the quality of a portfolio, and ultimately make wise decisions as to which projects should be pursued.
The Magnetic Resonance While-Drilling Tool: Theory and Operation
Authors: Prammer M. G. , Drack E. , Goodman G. , Masak P. , Menger S. , Morys M. , Zannoni S. , Suddarth B. , Dudley J.
Published: December 2007

The first Magnetic Resonance While-Drilling (MRWD) tools have been built and field tested. The hardware was designed to provide data compatible with the Magnetic Resonance Imaging Log (MRIL®) wireline tool in terms of processing and interpretation. The paper discusses the theory of robust MRIL measurements in the drilling environment and reviews the theory of T1 measurements. We report on the results of a field test in the Gulf of Mexico. The MRWD device logged the entire TD run from casing to TD and provided additional hydrocarbon-typing data in wiping mode over the target zones. Wireline MRIL data and conventional logs were used to verify the MRWD measurements.
Integration of Geology, Geophysics, and Numerical Simulation in the Interpretation of A Well Test in a Fluvial Reservoir
Authors: Raghavan R. , Dixon T. N. , Robinson S. W. , Phan V. Q.
Published: December 2007

The focus of this paper is the incorporation of geologic and geophysical data in the analysis of pressure tests in a fluvial reservoir. Using a 3,105,851 cell ‘porosity cube’ derived by seismic and well-log data, this work outlines the steps involved in developing a three-dimensional model with 7,128 cells that was used to estimate reservoir properties (permeability, skin, permeability-porosity relationship, reservoir connectivity, fault factor, etc.). The principal steps involved in developing the reservoir model include: identifying all points in the ‘porosity cube’ that were connected to the wellbore with porosities above a specified cutoff to identify the high- porosity channels and low-porosity overbanks,upscaling the ‘porosity cube’ to a reasonable size for welltest simulation while preserving pay thickness, pore volume, connectivity between high- and low-porosity materials, etc.,matching the observed pressure and pressure-derivative responses using a numerical simulator and a regression program to automatically adjust the reservoir permeability description.

A well test in a gas condensate reservoir is used to demonstrate the ideas outlined in this work. This approach allowed us to identify not only horizontal permeability but also vertical permeability. The issues that need to be considered and the conclusions that are derived on the basis of this work, differ significantly from conventional interpretations.
Gas Injection in Paleo Oil Zones
Authors: Skauge Arne , Hydro Norsk , Surguchev Leonid
Published: December 2007

In many large oil fields low oil saturation transition zones encompass significant hydrocarbon volumes. In some fields this retained oil below the water-oil contact in the water column is referred to as paleo oil. Gas injection represents one of the potential recovery methods to mobilize, displace and produce this remaining oil from transition zones.

The simulation model was built using geological description characteristic for the oil field water zone. The reservoir model for the water column above paleo water-oil contact was established based on core and log data from two wells. Down dip gas injection with vertical and horizontal wells was evaluated for drainage and recovery of paleo oil.

CO2 injection has been compared to flue gas and hydrocarbon gas. The immiscible or developed miscibility by CO2 injection process was more efficient due to compositional effects such as vaporization and swelling. Compositional simulation with fine grid vertical resolution in the reservoir model was performed. A large number of hydrocarbon components in the fluid description (17) were used in order to account properly for vaporization, swelling and gravity effects. The remaining oil saturation in the paleo zone may be significantly reduced by secondary and tertiary CO2 injection.

Simulations confirmed the formation of the tertiary oil bank and updip oil displacement. The CO2 liquid fraction in the oil bank reaches a level of about 50%. The oil viscosity in the moving oil bank is reduced significantly by dissolved CO2 compared to the viscosity of the original oil.

Simulations showed that high oil recovery factors could be achieved by gas injection in the transition paleo zone. The injection/production strategies can be further optimized to reduce high water-cut production period.
Real-Time Determination of Filtrate Contamination During Openhole Wireline Sampling by Optical Spectroscopy
Authors: Mullins Oliver C. , Schroer Jon
Published: December 2007

The key objectives of openhole wireline sampling are to identify desired fluids and to collect representative formation samples. Optical methods such as visible – near-infrared spectroscopy (NIR) are used to identify and quantify mixed oil, water, and gas flows in-situ during wireline logging. In wells drilled with oil based muds (OBM) or synthetic based muds (SBM), differentiating crude oil from the filtrate base fluid is critical. The widely used current practice is to measure the increase in fluid coloration (by NIR) vs. time to qualitatively assess the increasing fraction of crude oil with pumping time. Here, we describe new methods of utilizing NIR log data to provide quantitatively during sampling the %-OBM contamination in the extracted fluid. In addition, these methods allow prediction of contamination at future times during the sampling job, thereby determining the effectiveness of further pumping. The significant improvement in sampling efficiency is demonstrated with several log examples. Finally, using our methods, mud performance in the downhole environment can be monitored and optimized in subsequent jobs.
Equation of State of a Complex Fluid Column and Prediction of Contacts in Orocual Field, Venezuela
Authors: Smith Richard W. , Bard Wade A. , Lugo Claudia , Yemez Ivan , Guerini Agostino , Whitson Curtis H. , Fevang Øivind
Published: December 2007

Diligent management of a high-pressure gas injection program in a field with a complex column of hydrocarbon fluids requires reservoir modeling. It is important and necessary to perform a detailed study of the PVT samples including the evaluation of the fluid distributions and to define an equation-of-state (EOS) to be used in a reservoir model.

The Orocual field is located in the northern Monagas state of Venezuela and is owned and operated by Petroleos de Venezuela, S.A. (PDVSA), the national oil company of Venezuela. The field is characterized as a complex structure having more than 3000 feet of vertical hydrocarbon column. Fluids change from light gas in the top of the structure to condensate gas, to a near-critical transition fluid and volatile oil, to under-saturated oil at the bottom of the column.

Reservoir compartmentalization adds complexity to the field and structurally equivalent, non-communicating fluid regions exist. The dispersion of some sample characteristics versus depth was thought to be the result of non-representative samples. The ability to integrate the PVT data into the geological model adds another dimension in defining the structural complexities.

The paper demonstrates a technique to identify representative samples for use in developing an EOS, and for initializing fluids in place. A method is presented to adjust the component composition versus depth, providing consistent vertical composition distribution and compositional model stability. This method meets the objectives of matching field production observations. Also, a method is presented to quickly initialize a full field model using a 1-D compositional simulator to give full field model stability in an environment of high temperature gradient.

The final result is a 7 pseudo-component EOS with a single characterization defining the compositional gradient of the hydrocarbon column from gas to black oil. The method demonstrates that composition relative to depth can be predicted in those parts of the reservoir where samples do not exist, but where production and test data must be matched.

Other areas in northern Monagas state have similarly complex systems1. Many areas are only partially developed and can benefit by applying techniques presented in this paper to describe the fluids and to estimate gas-oil contacts.

Results of compositional simulation show a single EOS and vertical compositional variation reproduce the complex character of the field hydrocarbon column, matching field measured observations of saturation pressure (ps), gas-oil-ratio (GOR) and fluid densities.
Baseline Characterization of U.S. Exploration and Production Wastes and Waste Management
Authors: Petrusak R. L. , Freeman B. D. , Smith G. E.
Published: December 2007

The American Petroleum Institute (API) conducted a survey of onshore oil and gas exploration and production (E&P) operations and natural gas processing plant operations. The survey sought data for 1995 on current drilling practices, drilling and production waste volumes, and current practices for the management of wastes and produced water. API's survey was designed to update a similar survey of E&P waste management conducted a decade earlier. This paper presents the findings of the survey and compares the 1995 and 1985 survey results for the three main categories of oil and gas E&P wastes: Produced water – water brought to the surface with oil and natural gas,Drilling waste – rock cuttings, drilling mud, and other fluids produced as result of drilling a new wellbore,Associated wastes – various small volume wastes that include all other wastes "associated" with oil and natural gas production.

Between 1985 and 1995, the total volume of wastes generated annually by the oil and gas industry decreased by over 15 percent from 21.3 billion barrels in 1985 to 18.1 billion barrels in 1995. The decreased volume of E&P wastes generated is consistent with the general decline in E&P activity (lower oil production, fewer producing wells, fewer new wells drilled) which impacts the two largest volume waste streams -produced water and drilling waste. The survey results also demonstrate increased use of improved drilling and waste management practices during the past decade. For example, the results suggest a trend towards overall reduction of oily associated wastes, glycol dehydration wastes, and drilling wastes from operations using oil based mud. A significant, and growing, percentage of all E&P wastes (over 90 percent) are disposed of by injection.
Technologies and Possibilities for Larger-Scale CO2 Separation and Underground Storage
Authors: Holt T. , Lindeberg E. G. B. , Taber J. J.
Published: December 2007

International agreements on the need to reduce the emissions of greenhouse gases into the atmosphere may bring forward geo-storage of CO2. Several technologies are suited to recover CO2 from power production and industrial point sources. These emissions represent significant parts of the CO2 emissions in industrialized regions. Separation of CO2 from power plant flue gases, compression, pipeline transport and deposition will increase the electricity cost by approximately 50%, but the use of CO2 to recover additional oil may offer a significant value for large quantities of CO2. Underground storage in petroleum reservoirs and aquifers has a large capacity and is environmentally safe. On a long term the deposition capacity in oil reservoirs is limited, but at present, petroleum reservoirs represent significant sinks for CO2.

Underground storage of CO2 both in petroleum reservoirs and aquifers offers new business opportunities for the petroleum industry. The petroleum industry has a long time experience with all the operations and aspects involved with transport and injection of CO2 and other fluids into underground formations.
Fracture Fluid Damage to High-Permeability Gas Reservoirs: It Can Make A Difference
Authors: Robinson Bradley M. , Diyashev Iscander R. , Rahim Zillur , Wolhart Stephen L. , Salehi Iraj A.
Published: December 2007

A new study has been performed that focuses on the reduction in gas flow rates and production that can occur due to damage from fracture fluid leakoff in high permeability gas reservoirs. We found, in some cases, fluid damage to the formation during fracturing operations (i.e., Frac Packs) may be more severe than what has been previously assumed in prior studies. As a result, gas flow rates can be significantly reduced, especially in gas reservoirs with moderate levels of permeability; e.g., 10 – 50 md. The results of the study also showed that some fracture treatments are not achieving sufficient propped lengths to overcome near wellbore damage, thus compounding the problem and further reducing gas flow rates
Supercritical CO2 Extraction Applied to Oily Drilling Cuttings
Authors: Saintpere Stephane , Morillon-Jeanmaire Anne
Published: December 2007

With environmental concerns playing a growing role in the drilling industry, drilling waste disposal has become on unavoidable and important component of a drilling team’s scope of work.

By end of year 2000, sea disposal of OPF (Organic Phase Fluid) will be phased out from the British North Sea area. Cutting Re-Injection or Ship-to-Shore for thermal, solvent or inerting treatments will be the only acceptable alternatives for oily cuttings disposal.

The following paper presents an innovative approach to the complex problem of the separation of OBM from cuttings using Supercritical Carbon Dioxide technology (SCCO2). Above 73,8 bars and 35°C, Carbon Dioxide (CO2) exhibits special properties such as high density, high diffusivity and low viscosity, but above all, tremendous solvent properties regarding non-polar molecules such as hydrocarbons. This special state, sometimes referred to as the 4th state of matter, is widely known as the supercritical state. CO2 in supercritical conditions is already widely used in various industrial extraction processes, such as coffee bean decaffeination, fragrances and flavors selection or pharmaceutical molecules production.

A pilot unit capable of handling up to 500g of cuttings per batch and allowing supercritical CO2 steady circulation, has been developed to study the efficiency of the process. Tests have been performed on oily cuttings coming from various locations and different OBM Cuttings. Best extraction conditions have been optimized and the efficiency of the separation has been very encouraging: Residual Oil Contents (ROC), as low as 0.2 % (by weight of dry cuttings) have been achieved.

An evaluation on 2 larger scale units has also been made: a 6 kg static reactor and a 10 kg rotating autoclave (both dedicated to pre-industrial feasibility studies) enabled the evaluation of the efficiency of the treatment on North Sea OBM Cuttings. Residual oil contents below 1% have also been reached proving that scaling up the process, from hundreds of grams to several kilograms, is viable and practicable.

The industrial potential of this promising technology is currently under study. The application of such a technology could constitute a major breakthrough in the drilling industry, both onshore and offshore.
Field-Wide Variations of Wettability
Authors: Hamon Gerald
Published: December 2007

Core laboratory results are used to describe the variations of wettability Index and residual oil saturation to water within an oil-bearing consolidated reservoir. Core sampling is carried out to cover a large range of permeability ( from 1 mD to 1600 mD) and height above the initial water-oil contact (from 4 m to 175 m). The following experimental data are available: Twenty-six drainage and imbibition capillary pressure curves are measured at reservoir conditions, using reservoir fluids and both water-wet and oil-wet semi permeable membranes.Quantitative mineralogy and pore geometry by combined SEM and image analysis. Both bulk and pore wall mineralogy is available on some samples.

Typical mixed-wet imbibition capillary pressure curves are obtained. Experimental results illustrate strong trends between the amount of spontaneous imbibition, the wettability Index to water and the residual oil saturation on one hand and both the structural position and the permeability of samples on the other hand. Relationships with pore wall mineralogy are rather weak.

The combined effects of structural position and permeability on wettability result in unusual variations of the forced imbibition capillary pressure curve within the reservoir. The plateau of the Pc curve is weakly dependent on permeability. A new way to extrapolate forced water/oil imbibition Pc curves is proposed.
Emulsion Separation Index: From Laboratory to Field Case Studies
Authors: Kokal Sunil , Wingrove Martin
Published: December 2007

Quantifying oil-water or emulsion separation has always been difficult. This is due, in part, to the numerous factors controlling oil-water separation. This paper describes a new method developed at Saudi Aramco for the quantification of oil-water separation process. It is designated as ESI or Emulsion Separation Index and it was developed to measure emulsion stability. This index has been used to select and screen demulsifiers and to quantify the effect of various factors that affect oil-water separation including temperature, shear, asphaltene content, watercut, demulsifier dosage and mixing different crudes. Its use has eliminated some of the ‘art-work’ associated with demulsifier selection and diagnosing emulsion treatment problems.

This paper also describes three field case studies where the ESI was used to select the best demulsifier, diagnose, and ultimately solve emulsion related problems during oil production. The first field study is from the largest onshore oil field in the world. The emulsions from this field were being stabilized by inorganic scales and organic asphaltenes. The paper describes how the ESI was used to diagnose and resolve the problem. The second field study is from the second largest offshore field in the world. Here extremely tight emulsions were forming and plugging the separation equipment offshore. These emulsions contained 70–90% water and were very viscous. Their deposition in the separation equipment was resolved by using recommended demulsifiers and performing ESI tests in the field. The demulsifier dosage was also optimized using these tests. The third field case study is from another large offshore field that produces from seven different reservoirs. The properties of the crudes from the seven reservoirs vary significantly. These properties provide an interesting case of operational problems in oil-water separation including increased incidents of arcing/shorting in the separator, tripping of equipment and increased demulsifier consumption. The factors affecting oil-water separation were quantified using ESI. The results show a strong correlation of asphaltene content in the crude oil with ESI or emulsion tightness. Recommendations were made for reducing and optimizing demulsifier dosage by adding chemical additives. Many lessons learnt in these field studies are applicable to any crude oil treating facilities.
Unique Multilateral Completion Systems Enhance Production While Reducing Cost and Risk in Middle East Offshore Wells
Authors: Demong Karl
Published: December 2007

Most multilateral wells in the Middle East have been completed as non-access single-selective or limited-access, dual-selective wells. These configurations improved production by achieving increased reservoir exposure at reduced operating cost by hitting two or more targets from a single well. Previous applications had a disadvantage in that these configurations often limited the operator’s ability to monitor and enhance well production or perform effective workover operations. Advances in multilateral (ML) completion technology for new or existing wellbores have now resolved some of these difficulties with unique completion systems. These have the capability to mechanically connect laterals to parent wellbores and allow segregated production and intervention at any time in the life of the well. Operators in Qatar, Saudi Arabia, and the United Arab Emirates have applied these innovative techniques, providing a greater variety of options to satisfy the completion, workover, and intervention requirements of dual producing wells.

This paper will discuss case histories in which dual-segregated completions with and without pressure-isolated junctions were developed and used. The completions were run in both new and existing wells and in both primary well construction and workover scenarios. In each case, the operator’s requirements were satisfied. The success of these multilaterals has broadened the scope of applicability for duallateral completions and workovers.

The new ML concepts offer the following enhancements: Since the completion configuration is dual segregated, it allows segregated production and segregated through tubing re-entry into two reservoirs.New procedures for running the packers into the lateral have been developed. Construction of the pressure-isolated junction can commence during initial completion or during workover operations. This can reduce the cost of the initial completion and reduce some of the risk of debris problems.Dual segregated completions can be installed as part of the initial completion or implemented later during a workover operation. If there are production problems with a conventional completion or a junction leak in a commingled completion, the dual segregated completion can be installed as a remedy that also supports production logging and any rigless interventions that may be required.
Development of a Continuous Permeability Measurement Using Wireline Logging Methods and the Resulting Impact on Completion Design and Post-Completion Analysis
Authors: Kerchner S. , Kaiser B. , Donovan M. , Villarreal R.
Published: December 2007

In the exploration and development of oil and gas reservoirs, one of the most critical parameters to measure or calculate is permeability. The permeability of a reservoir can have a dramatic impact on the initial completion and stimulation design and a significant influence on reserve calculations.

The methods traditionally used today to acquire formation permeability can be expensive and time consuming. These methods include whole corerotary sidewall and percussion corespressure transient analysisproduction history matching.

Obtaining a whole core is risky and can be prohibitively expensive. Acquiring rotary sidewall and percussion cores also carries an inherent risk and is time consuming and expensive. Also, core analyses do not always reflect representative permeability at downhole conditions and provide a small statistical sampling of the zones of interest. The preferred pressure transient method involves a flow period followed by a pressure buildup test, which involves flowback crew and equipment expenses, possible workover expenses for running tubing, and delays post stimulation production to sales. Similar delays are inherent in production history matching.

A continuous permeability measurement obtained through wireline measurements is proposed as an alternative to these traditional methods. This permeability is available immediately and can be used to proactively estimate reserves and initial production and to design and evaluate the effectiveness of various stimulation programs. The most economic design can then be selected.

This paper describes a project undertaken by Conoco and Schlumberger. The project objectives were to develop a field-specific method to reliably estimate permeability using wireline logging methodsdemonstrate how this information impacts economic and engineering considerations related to the hydraulic stimulation programdescribe the importance of knowledge of permeability in post-audit analysesrecommend best-practice guidelines for use of a particular method to obtain permeability.

This paper covers the project methodology, field data collection and interpretation, completion design, execution, and evaluation, and the project well results.