bluuebunny/crossref_metadata_2025 huggingface dataset:
Drilling-Derived Rock Strength Can Simulate Upcoming Well Performance
Authors: Fazaelizadeh M. , Rashidi B. , Hareland G.
Published: February 2011

A drilling simulator has been used during the past four years to improve the drilling performance in Western Canada. Rate of penetration improvement and subsequent cost and time reductions are the key elements for drilling these wells. A drilling simulator is required to generate the "Apparent Rock Strength Log" (ARSL) using available offset well data. The ARSL calculation is based on using inverted Rate of Penetration (ROP) models for different bit types, reported bit wear, lithological information and pore pressure in addition to the drilling parameters. The generated ARSL can be modified and correlated for different and new formation tops for planned wells.

The obtained ARSL logs for the wells in the same field have shown an acceptable overlay for the common lithologies using different bit runs and drilling parameters. Furthermore, it can be shown that the ROP match with the new simulated ROP in the same well applying another well's drilling parameters once their ARSL are adjusted. It has been shown that a typical cost reduction can be achieved for the planned wells utilizing the drilling simulator when previously drilled wells exist. The effect of using the combination of different bit runs and drilling parameters can also be explored through use of the simulator. In this paper, a study was conducted for two wells in an Albertan, Canada field to investigate the effect of using the bits used in a well to reduce cost and optimize the next well.

The ARSL logs of two wells were separately obtained and compared. The comparison between the new simulated ROP for the first well, using another well's drilling data, and the available ROP for the second well is also discussed. Final results are showing an acceptable match obtained for ROP values as well as for the corresponding drilling time and final bit wear status in each of the bit run sections. Utilizing the simulator in these type wells shows a significant cost and time reduction potential and can be helpful to apply in preplanning analysis for new wells to be drilled using previously utilized bit types and designs.
Piltun ‘Sub-Arctic’ Offshore Integrated Oil and Gas Development
Authors: Shlyakhova Anna , Kasumov Timur , Jones Malcolm K. , Morgan David
Published: February 2011

The Piltun integrated oil and gas development is a part of the Sakhalin-2 Phase 2 project, and provides a significant portion of Sakhalin Energy's annual revenue through the development of the Northern part of the massive Piltun-Astokhskoye field. This offshore field was discovered in 1986, off the coast of Sakhalin Island, in Russia's Far East. This remote field is in an environmentally sensitive area with an extreme “sub-arctic” climate and a history of seismic activity. The easier part of the field (“Astokh”) was developed first with seasonal production, making it Russia's first offshore oil development, but the multilayered Piltun area retained a significant degree of uncertainty and required a different development approach. First oil was achieved in 2008 and within one year the development produced its 10 millionth barrel of oil, and was benchmarked as “best in class” on drilling performance and recorded a number of “firsts” in the Russian Oil and Gas Industry with its initial smart water injector well.

This paper provides an overview of the challenges of developing this field, the successful reduction of major uncertainties and the multi-disciplinary approaches and use of technology that ensured an extremely successful first start-up of operations.
Results of New Drilling Technology Application on the Development of Verkhnechonskoye, a Complex East Siberian Field
Authors: Wilson K. , Shokarev I. , Small J. , Akhundov E.
Published: February 2011

This paper will describe results of the application of new drilling technology on the well cycle time and production results in the Verkhnechonskoye (VC) Field - one of the largest fields in Eastern Siberia (estimated >200 million tons of oil reserves) with TNK-BP & RosNeft as VCNG's main (company operator) stock holders.

The Drilling & Production environment in the VC field is very challenging, drilling encounters a range of issues from, low ROP in hard dolomites, risk of stuck pipe in unstable shales, high stick'n’slips, to unpredictable BHA behavior in hard gravalite zones, these challenges are compounded by the complex geology of this hetrogenous field. To meet the FDP schedule of 500+ horizontal wells (during 2007-2021) and the production targets (up to 10 million tons of oil per year) it was necessary to significantly improve the well construction time and maximize the net to gross pay ratio of the horizontal section.

VCNG drilling department partnered with Schlumberger and over a period of 24 months completely redesigned the drilling programs and data acquisition methods. The subsurface team developed a methodology to significantly improve drilling efficiency using Schlumberger Rotary Steerable Systems. While the net to gross of the horizontal sections was improved by utilizing high tech Logging While Drilling tools and Geosteering the well to overcome the geological uncertainties.

The initial well cycle for a development well completed using positive displacement motors and standard directional techniques averaged 63 days. The horizontal section of the well was exhibiting a net length to gross reservoir exposure of approximately 30%. By July 2010 the well construction cycle was reduced to 22.3 days including an addition 100+ m of lateral section and the net to gross was 70+% with corresponding higher production.

These latest drilling benchmarks and lessons learnt from one of the first major development projects in the heart of Eastern Siberia will be reviewed in this paper. Information on the basis of well design, the theoretical drilling limit, and the application of drilling technology coupled with information on work processes and best practice will be pertinent to other Eastern Siberia development projects.
Remedial Cementing at High Temperatures (Case Study: Oilfields of Rosneft-Stavropolneftegaz)
Authors: Sakhan A.V. , Chegodaeva A.A. , Gorbunov V.V.
Published: February 2011

Oilfields of Rosneft-Stavropolneftegaz have basic distinctions, such as high reservoir temperatures, up to 1600C, and low depths, down to 3,500m, and old casing strings, where cement sheath is often absent, which require application of special technologies and compounds to be efficient for these conditions.

In prior years all remedial cementing in Rosneft-Stavropolneftegaz, irrespectively of water trouble sources, were executed with cement slurry only. We have selected technologies and compiled application matrices for elimination of behind-the-casing flow (reverse cementing) and flow string leaks (flow string leak repair) in high temperature environment.

In 2008-2009 the laboratory and pilot testing of technologies was performed, and new process was tested during water inflows elimination in the wells with high injection capacity. The risks are determined for planning and execution of remedial cementing, and the ways of finding solutions are offered.

In general the total success of remedial cementing in 2009 in Rosneft-Stavropolneftegaz amounted to 70%, which twice exceeds this index for the year 2008. The average growth of flow rate for 11 wells amounted to 24 tones/day. It was possible owing to: Correct selection of candidate wells;Opportunity to select various plugging materials for specific task, i.e. using materials other than cement slurry;Selection of optimal flow charts for cementing process execution.

The successfully tested technologies are potentially applicable within the Company in 130 wells in the fields of Rosneft- Stavropolneftegaz, Grozneftegaz and Dagneft.
The Research of Influence Sea Stationary Platforms Structure Features on Strength Properties of Basic block
Authors: Guseynova N. I. , Guseynov I. Q.
Published: February 2011

Offshore stationary platforms for oil gas and recovery (OSP) are established on a continental shelf of the seas and oceans. In Azerbaijan wide development of sea oil fields on Caspian Sea has begun in the late forties with a construction of sea platforms and the individual island bases around "Neft Dashlary" and the "Gurgjany-sea".

Design OSP is possible to be classified to following features: on conditions of basing – pile, gravitational, pendular; on a material - metal, ferroconcrete, combined; on type - through and continuous. Now, on Caspian Sea the most widespread are OSP of pile design.

The basis pile OSP represents an underwater bearing spatial trellised design from the metal tubular elements, attached to a sea-bottom by means of piles. Piles provide perception of all external influences: waves, currents, a wind and operational loadings. Attached by means of piles to a sea-bottom the tower supports an artificial islet on which a derrick, workshops, a helicopter platform, premises and so forth are placed That, as a rule, are the unique expensive constructions reaching of depths 200 – 300 m and more, at width of the basis of an order of 70 m. Cost them, beginning approximately with depth of 60 m, grows proportionally to a depth square exhausting. And, cost of operational platforms with the equipment at development of deep-water deposits can make 50-60 % from an overall cost of arrangement of all deposit.
New Solution: Operational Field Control of Pipelines Corrosion Rate
Authors: Sukhnat Egor
Published: February 2011

The key target of pipelines operation in oilfields is their failure-free service throughout their useful life. According to Oilfield Pipelines Integrity Strategy, inhibitors are said the main corrosion control solution. The amount of inhibitor-protected pipelines keeps growing across TNK-BP from year to year thus allowing the Company to considerably reduce the pipeline failure rate.

Corrosion monitoring is an important tool of inhibition efficiency tracking. It identifies changes in corrosion rate and other parameters that characterize aggressive effect of the medium. By doing so, corrosion monitoring signals of the changes in pipeline operating conditions or the variances in inhibition processes. Corrosion monitoring confirms that as a result of inhibition, pipeline corrosion rate stays acceptable and poses no threat to pipeline integrity.

Corrosion driving factors are too many and, thus, it seems impossible to find any good-for-all method to forecast pipeline integrity or assess efficiency of the activities performed. The operational methods of measuring corrosion rate and its changes in time are the most informative which makes them more widely used in corrosion monitoring.
Well Path Design Optimization Under Geological Uncertainty: Application to a Complex North Sea Field
Authors: Schulze-Riegert Ralf , Dong Ma , Heskestad Karl L. , Krosche Markus , Mustafa Hassan , Stekolschikov Konstantin , Bagheri Mohammad
Published: February 2011

Well placement and design under geological uncertainties represents a major risk for field development processes. Recent enhancements in geological modeling tools allow reservoir geologists to generate large numbers of alternative 3D models which honor available log and seismic data. For subsurface engineers such models behave quite differently which will impact well design and field development scenarios. Including alternative geological realizations in a manually optimized development plan has proven to be cumbersome and very time consuming. In practical cases, a single reference model is often used as a basis for the dynamic model which creates a major risk of underestimating static uncertainties.

This paper presents a workflow for well path design and optimization under geological uncertainties. Well path screening methods are developed for fast evaluation of alternative well designs in a heterogeneous reservoir model. The method is applied to horizontal well designs including multiple design points for a trajectory honoring geological and technical constraints.

The introduced workflow is capable of handling a large number of design options. Efficient parameterizations of well design parameters in target regions are chosen to limit the introduction of constraint handling methods. Static and dynamic simulations generate performance indicators. A performance overview is supported by the application of experimental design techniques and optimization processes for this study are supported by evolutionary algorithms. Alternative geological models are included in an integrated approach to generate risk profiles representing geological uncertainties.

The workflow is applied to a North Sea condensate field which has two main formations of interest. Information from an exploration well indicates that the uncertainties are related to sand connectivity and net sand content. The specific objective of the case study is to find optimum well positions and designs for horizontal wells by maximizing cumulative gas production. All well candidates are evaluated on the basis of three risked geological realizations which represent a base-, conservative- and optimistic case.

A well screening and well production optimization workflow is developed and successfully applied to complex well designs. Practical experience in a real field application underline benefits for generating risked cumulative production profiles in an extended risk assessment.
Discovery of New Petroleum Basin Offshore of Sakhalin Island
Authors: Bychkov A. V.
Published: February 2011

The Sakhalin oil and gas area occupying the territory of Sakhalin Island and the water area of the adjacent shelf includes completely or partially the range of sedimentary basins (Fig. 1): North-Sakhalinsky, South-Sakhalinsky, Deryuginsky (the western board), West-Sakhalinsky (the eastern board). The oil explorations began in the region nearly 100 years ago and by the end of the last century there was established the industrial oil-and-gas content of the North-Sakhalinsky (1911), the South-Sakhalinsky (1971) and the West- Sakhalinsky (1986) basins. The vast majority of the deposits (70 from 75) were explored in the structures of the North-Sakhalinsky basin. Four small deposits of gas were opened in the structures of the Anivsky anticline zone in the territorial part of the South-Sakhalinsky basin, the small gas deposit was prospected in the West-Sakhalinsky basin on the per-sakhalinsky shelf. Just the first well bores drilled in the shelf in the North-Sakhalinsky basin provided the great openings (within the period of 1977-1979). In the ensuring 15 years, the large gas-condensate-oil deposits, as well as the unique oil-gas-condensate deposit were opened, on the basis of which there had been created the projects on oil and gas production, such as "Sakhalin-1?? and "Sakhalin-2?? Projects.
Independent Verification of Safety Critical Elements
Authors: Marty Julien , Theys Sophie , Bucherie Christian , Bolsover Andy , Cambos Philippe
Published: February 2011

The main objectives of “Independent Verification of Safety Critical Elements” are to help substantiate that current oil and gas best practices are used, to provide assurance that facilities have been designed to operate safely throughout and to ensure that all Health Safety and Environment risks have been managed to acceptable / As Low As Reasonably Practicable levels. It anticipates the lack of applicable laws or standards, especially in the case of new environments. This approach, which was initially introduced in the United Kingdom after Piper Alpha disaster in 1988, is now becoming an industry standard worldwide.

Offshore Russia offers extreme (remote and arctic) conditions which are a challenge today. This, and the lack of Russian Federation laws applicable to the control of Major Accident Hazards, may represent an issue regarding Health, Safety and Environment for operating companies.

This paper will describe the history of independent verification, and particularly show its application on the Front End Engineering Design stage of a project lead in Russia. It will highlight the regulatory differences and the value of a goal setting process in such situations. This article shows an example of implementation in a country unfamiliar with independent verification.
A New Technology for Filter Cake Removal
Authors: Rostami Ameneh , Nasr-EI-Din Hisham
Published: February 2011

Horizontal and maximum reservoir contact (MRC) wells are intended to increase productivity and minimize water production due to water conning. Their complex geometry makes cleaning up of drilling fluids filter cake a difficult task. It is hard to distribute the acid uniformly over long horizontal sections. Poor acid distribution occurs during matrix acidizing. Coiled tubing cannot reach the total depth of the well because of some limitations such as large washouts, length of the reel and diameter of the coil, which make acidizing horizontal wells ineffective. Available chemical methods of removing filter cake like mineral acids, esters, oxidizers, chelating agents, and enzymes are limited at certain conditions.

This paper introduces a new method for filter cake cleaning using a self-destructing water-based fluid to drill long horizontal and MRC wells, which results in higher productivity. This fluid is a water-based mud that is weighted with calcium carbonate and has both functions of drilling and completion fluids, can reach total depth of MRC wells. It has the ability to effectively stimulate the whole horizontal sections after drilling. This can result in significant cost savings by elimination of acidizing using coiled tubing or any other means and improvement in filter cake removal and thus enhances performance of the treated wells.
Commercial Application of Dual Completion Technology
Authors: Garifov K.M. , Glukhoded A.V. , Ibragimov N.G. , Fadeev V.G. , Zabbarov R.G.
Published: February 2011

TATNEFT’s fields are, for the most part, multilayered with two and more development targets, which makes dual completion technology an optimal reservoir management solution.

The Company’s first dual completions date back to the 1960-ies, however, deficiency of oilfield hardware, especially, packers, as well as lack of production control equipment prevented commercialization of this technology.

The last decade witnessed a revived interest to dual completions.

TATNEFT has been successfully implementing dual completion technology since 2003. Different dual completion systems to meet different production conditions have been developed.

Completions with one and two strings of tubing using sucker rod pumps have found wide application. The singletubing-string completion system is used to produce from two segregated productive zones isolated with a packer. Though the well stream is commingled, methods to determine production rates, water cut, and bottomhole pressure for each target are available.

The two-tubing-string completion system has been known since 1950-ies, and in its present configuration includes the in-house dual-string wellhead equipment, parallel anchor, and M1-X production packer.

For more prolific wells two different production systems based on combination of electric submersible and sucker rod pumps are used: with commingled and non-commingled production. Production options for high viscosity oil provide for progressing cavity pumps. Also, dual completion technologies for injection using one and two packers have been developed.

By now, dual completion systems have been installed in more than 500 production and injection wells with incremental ultimate recovery exceeding one million tons of oil.

Dual completion technology has proved its efficiency for increase and stabilization of the production level, and it is one of the priority investment projects of the Company. TATNEFT plans expanding scope of the technology application, development of new dual completion systems, and improvement of existing ones.
Restimulation of Unconventional Reservoirs: When are Refracs Beneficial?
Authors: Vincent M. C.
Published: February 2011

Restimulation treatments have been attempted in a wide variety of reservoirs, and more than 140 papers have been published documenting the success and failure of these efforts. A database of these published examples has been compiled and analyzed to identify the mechanisms responsible for production improvement following restimulation with propped fractures (refracs). A portion of this database was recently published (Vincent 2010), and specific field examples were highlighted to demonstrate that refrac treatments can improve production by numerous mechanisms including:

– Enlarged fracture geometry – Improved pay coverage through increased fracture height in vertical wells – Greater lateral coverage in horizontal wells or initiation of more transverse fractures – Increased fracture conductivity compared to initial frac – Restoration of fracture conductivity loss due to embedment, cyclic stress, proppant degradation, gel damage, scale, asphaltene precipitation, fines plugging, etc. – Increased conductivity in previously unpropped or inadequately propped portions of fracture – Use of more suitable fracturing fluids – Reorientation due to stress field alterations, leading to contact of "new" rock

This paper will briefly review restimulation attempts in six Canadian reservoirs of interest to the local audience, and will then present a more detailed review of restimulation of horizontal wells in the unconventional Bakken oil formation. In addition to a summary of published results, this paper will introduce a significant amount of previously unpublished data regarding refrac treatments of horizontal laterals completed in the Middle Bakken. This study will identify several additional concerns and opportunities with restimulating horizontal wellbores that were not previously identified in literature reviews. This organized summary of field results and references will provide significant value to readers evaluating or designing restimulation treatments.
A Numerical Study of the Effects of Packer-Induced Stresses and Stress Shadowing on Fracture Initiation and Stimulation of Horizontal Wells
Authors: Singh I. , Miskimins J. L.
Published: February 2011

"Stress shadowing", where the creation of hydraulic fractures affect the stresses in certain parts of the reservoir, has the dual effect of assisting and hampering the generation of hydraulic fracture stimulation in horizontal wells. In this paper, the stress contrast and pressure profiles around the near wellbore regions of a horizontal wellbore with the presence of packers and hydraulic fractures are investigated. This was accomplished by using a finite element software package where the numerical results of the behavior of the stress envelopes and stress shadowing phenomena could be evaluated and different sensitivities analyzed.

From the results obtained, it is concluded that packers with higher pressure generation allow for easier fracture initiation as compared to packers with lower pressure generation. Additionally, modeling indicates that the weakest point for fracture initiation in a wellbore with a packer is at the ends of the packer. When two packers, with differing pressure generations, are placed in the wellbore, fracture initiation will occur near the packer with the higher pressure generation. Finally, it can be concluded that in areas of high stress concentration, the ability to generate hydraulic fractures is reduced as compared to areas of low stress concentrations.
Pseudo-components for Nigerian Heavy Oil and Bitumen
Authors: Lawal Kazeem A. , Adenuga Ademola O.
Published: February 2011

In composition and behaviour, bitumen and heavy oil are more complex than conventional oil; hence they pose greater challenges for reservoir and process simulations. This notwithstanding, one practical approach for constructing efficient fluid-property models is the lumping technique, entailing the use of pseudo-components (PC). However, this is not so straight-forward, especially for these unconventional hydrocarbons whose compositions are typically available as chemical aggregates (saturates, aromatics, resins and asphaltenes) rather than the common and more convenient pure components.

This paper highlights key issues affecting construction of PC’s in general, and limits them to heavy oil and bitumen. It argues that the number and characters of PC’s should be influenced by prospective method of development, processing as well as the nature of fluids the crude would contact. Hence, process-based PC schemes are proposed for the Nigerian unconventional crudes. As an example, the number of components required for a thermal process using asphaltene-precipitating injectant (e.g. CO2) and that of a process based on steam, a non-precipitant, is shown to differ. Similar distinctions are indicated between thermal and solvent-based processes.

For some reference conditions, it is demonstrated that the Nigerian heavy crude can, in its simplest form, be reasonably represented as a single-component and up to five components where it is likely to undergo more complex processes or when greater details are necessary. With minor modifications, the proposed schemes should be adaptable to heavy crudes elsewhere.
Applied Strategic Dependability Functions and Models for Effective Asset Integrity Management in Organization
Authors: Arhagba Arierhe
Published: February 2011

Abstracts

At a time like this, a time of Global Economic Meltdown, financial and general economic recession, is a time to be more innovative, and find new ways of adding value to our overall corporate performance portfolio. A paradym shift in areas of asset integrity management that has largely centred on systems reliability management approach becomes an imperative.

In this paper, a dependability model is formulated to enhance our asset integrity management. This is actually a re-engineering of the entire process of systems asset integrity management and it is organization specific.

A whollistic system information bank is robustly entrenched in the maintainability and availability functions which are dependability and capability functions. Then, applied strategic dependability functions and models for effective and efficient assets integrity management in organizations are a necessity for corporate survival.

The paper emphasis systems audit of all the financial elements to ensure cost effectiveness and quality assurance of such specifications. Then a thorough process re-engineering of all the existing asset integrity management processes and procedures becomes a necessity for effective and efficient system overall performance.
Prediction of Volumetric Sand Production and Stability of Well-Bore in a Niger-Delta Formation
Authors: Adeyanju O. A. , Oyekunle L. O.
Published: February 2011

Nigeria’s Niger-Delta province has been identified as one petroleum system- The tertiary Niger-Delta (Akata-Agbada) petroleum system. Almost all the petroleum resources currently are produced from the sandstone species within the Agbada formation. Also turbidite sand in the upper Akata formation is a potential target in deepwater offshore and currently producing interval onshore. This paper presents a mathematical model to simulate sand production from petroleum reservoir subject to an open-hole completion. A coupled reservoirgeo-mechanical model was used to predict the volumetric sand production and associated wellbore stability. The model is based on mixture theory with erosion. The Representative Elementary Volume (REV) composes of five phases - solid matrix, fluidized solids, oil, water, and gas phase was chosen. The model also incorporates the reservoir drawdown pressure, rock failure criteria, rock types and field condition. Analytical solution of sand displacement processes is also highlighted. Results show that the magnitude of sand production is strongly affected by the flow rate, the confining pressure, the pressure drawdown and the fluid viscosity. The determined ratio of the productivity index to the saturation of the fluidized solid can be correlated to determine reservoir formation type during sand production, and predicting the wellbore stability. The model has a higher degree of validity for light and medium crude oil flow which possesses moderate lubricating properties, and therefore erosion of sand particles during production highly depends on flow rate.
A Review of Water Shutoff Treatment Strategies in Oil Fields
Authors: Joseph A. , Ajienka J. A.
Published: February 2011

Management of unproductive water has been a major challenge facing the hydrocarbon industry. It was estimated that about 210 million barrels of water are produced daily accompanied with 75 million barrels (11.9 million m3) of oil worldwide. Consequently, mechanical, chemical shutoff and other water reduction techniques have been developed and deployed to curb the menace in the hydrocarbon industry.

In this study, a review of the water shutoff treatment methods and reduction techniques in the industry was made. The major sources of water problems were identified and categorized into four major groups in order of treatment difficulties. A mechanism for attacking excess water production is also developed to enhance the application and success rates of water shutoff treatments and the latest technological advancements to make water shutoff treatments most viable is highlighted as well.

Five case studies were evaluated with published data to investigate success and failures after treatment using WOR, water cut, productivity change, oil gain and the period of sustenance.

The study reveals that the level of success is not just a function of the type of treatment deployed but routine diagnosis of the problem and that combined treatment proved to be the most efficient and sustained method.
Unhealthy Effects of Gas Flaring and Wayforward to Actualize the Stopping of Gas Flaring in Nigeria
Authors: Anosike Chikaodi R.
Published: February 2011

Nigeria flares more natural gas associated with oil extraction than any other country on the planet, with estimates suggesting that of the 3.5 billion cubic feet (100,000,000 m3) of associated gas (AG) produced annually, 2.5 billion cubic feet (70,000,000 m3), or about 70% is wasted via flaring. One of the greatest is the release of large amount of methane which has very high global warming potentials. The methane is accompanied by the other major greenhouse gas, carbon dioxide of which Nigeria was estimated to help emitted more than 3,438 metric tons in 2002, accounting for about 50% of all Industrial emissions in the country and 30% of the total CO2 emissions. This paper discussed some of the harmful effect of the gas flared on the livelihood of the communities and solution to actualize the stopping of gas flaring in Nigeria. Some of the harmful effects on the health and livelihood of the communities includes the release of variety of poisonous chemicals, just some of combustion by-products include nitrogen dioxides, sulphur dioxide, volatile organic compounds like benzene, toluene, xylene and hydrogen sulfide as well as carcinogens like benzapyrene and dioxin. Humans exposed to such substances can suffer from a variety of respiratory problems. Therefore in other for Nigeria as the giant of Africa to meet the worlds energy demand and supply, a quick response to utilizing natural gas should be made at least by concentrating in the liquefied natural gas LNG project which is targeted at foreign and local market, as a source of energy, also can be used as community projects and as well as re-injecting to enhance oil recovery.
Using an Automated Approach To Reservoir History Matching and Property Selection in Material Balance Modeling
Authors: Chinedu Onyeizu , Jye Collins , Tuitjer Eric
Published: February 2011

Petroleum engineers use material balance modeling and analysis for a high level understanding of the reservoir performance, drive mechanism and estimation of volumes in place. An intrinsic aspect of this analysis is to obtain a close match of the reservoir pressure behavior based on knowledge of production history, reservoir rock and fluid properties.

Material balance (MBAL) is a one dimensional approach and therefore difficult to generate a unique solution. This is especially the case when the field is in its early production life or there is significant uncertainty surrounding variables such as fluid properties and aquifer influence. To deal with this challenge, an automated concept has been developed using Petroleum Experts MBAL™ software. The concept processes a combination of subsurface scenarios to determine a range of solutions that mimic the reservoir pressure behavior. It uses a batch fit approach to generate multiple solutions within a given uncertainty range. The quality of each solution can be quantified through an automated calculation of the percentage error with history data at specific time steps.

In this paper, reservoirs within Benin River and Opuekeba fields are used to demonstrate the capability of the tool to select a number of history matched solutions. Each providing an outcome for Stock Tank Oil Initially In place (STOIIP). Current Oil-Water Contact (COWC) and Transmissibility.
Practical Guidelines for Predicting Sand Production
Authors: Osisanya Samuel O.
Published: February 2011

The control of formation sand is the principal producing problem of oil and gas fields producing from recent clastic sediments. Sand control is very important as the value of non-renewable oil reserves increases and cost of remedial work skyrockets. Sediments of the Pliocene and younger Tertiary ages are particularly troublesome, and sand production problems may be expected whenever wells are completed in unconsolidated reservoirs. Sand failures may also occur in older formations when in-situ rock strength is reduced by poor completion and production practices.

Several factors lead to sand production. The most critical factors are formation strength, changing in-situ stresses, and fluid production rate. The problems resulting from sand influx include abrasion of downhole tubular/casing, subsurface safety valve and surface equipment; casing/tubing buckling, failure of casing or liners from removal of surrounding formation, compaction and erosion; and loss of production caused by sand bridging in tubing and/or flow lines. Also, the cost of handling and disposing of produced sand is expensive and troublesome, especially offshore, where solids must be removed from surface facilities on platforms and transported to approved disposal sites to mention a few.

There are several methods for predicting sand production. The methods include use of production data, well logs, laboratory testing, acoustic, intrusive sand monitoring devices, and analogy. The methodologies are described in details and the data needed for predicting sand production are enumerated. The techniques described in this paper are supported with examples and case studies from regions around the world known for sand production.
Effect of Cementation on Mechanical Properties of Reservoir Rocks and Hydrocarbon Production
Authors: Ghadami Jegarluei S. , Moazzeni A. R.
Published: February 2011

Porosity and permeability are two important reservoir rock properties intensively affect quality of the reservoir. Various parameters affect these two factors which cementation is the more important. Measuring cementation accurately the place of entrance of hydrocarbon to the reservoir can be determined and permeability and porosity of the reservoir rock can be qualified. Since rock mechanical properties of reservoir rocks are severely impacted by cementation and rock mechanical properties of the rock are the important parameters for the mechanical reservoir modeling, which is used for well bore stability analysis, sand production prediction and finally studying the compaction of reservoir rock importance of this phenomena can be denoted. In this study diagenesis of lime stone and sand stone, effect of cementation on oil production and methods of increasing production when cementation is poor would be considered.
Experimental Investigation Of Specific Energy Of Rocks By Low Power Laser Drilling
Authors: Ashena Rahman , Ashena Rahim , Nabaei M. , Habibnia B. , Taee B.
Published: February 2011

Specific energy is the amount of energy required for a specified volume of rock to be destroyed. This is a normalization method used to compare the efficiency of destruction of rocks. Low power laser beam of Free Electron Laser (FEL) has been shown in literature to be used to penetrate different reservoir carbonate rocks and shales. The corresponding specific energies and ROPs are measured when a work in this field is performed.

laser beam is shown to be capable of drilling boreholes because of the high energy it can create. Laser is shown to drill shales while preventing the clay swelling problem prevailing when water is in contact with shales. Laser can also increase the accuracy of perforation of casing strings. In works like, the core samples to be tested are usually taken from fields and analyzed.

Comparison of different laser modes in terms of specific energy and ROP increase has been investigated and presented as a literature review which has not been accounted for in many previous works. As the future work, shape and rock type should be considered although there exists many works in literature wherein these parameters have been neglected.
Modeling the Perforation Stress Profile for Analyzing Hydraulic Fracture Initiation in a Cased Hole
Authors: Fallahzadeh S. H. , Shadizadeh S. R. , Pourafshary P. , Zare M. R.
Published: February 2011

Hydraulic fracturing has been used for many years in order to stimulate the oil and gas wells for improving the reservoir production. Many investments are allocated for hydraulic fracturing all around the world to develop hydrocarbon resources. Most of them are done for cased holes which some of them do not significantly improve the hydrocarbon production. The main reason is improper fracture initiation and complex near-wellbore fracture geometry which is a challenging problem.

In cased holes, the perforations are the only connection between the well and the reservoir, therefore the fracture initiates somewhere in the perforation. Understanding the stress distribution around the perforations is the key for analyzing the fracture initiation mechanism and thereby the near-wellbore fracture geometry. In this paper new analytical formulas are derived and applied along with numerical methods to simulate the stress profile around the perforations.

Having analyzed the perforation stress distribution, it is possible to understand the mechanism of fracture initiation and consequently improving the near-wellbore fracture geometry. Results of this model are presented at some in-situ stress regimes, cement and rock properties, and also perforation and well parameters. It is concluded that, at any specific stress regime, there is an optimum well design and completion, and also perforation orientation, which leads to lower fracture initiation pressure as well as better fracture orientation geometry in terms of less near-wellbore fracture tortuosity. Therefore, better connection can be developed between the borehole and the reservoir formation.

The importance of this model is its ability in analyzing the stress profile along the perforation tunnel, so more realistic fracture initiation pressure and fracture geometry can be estimated for better well completion and perforation design.
A New Multi-Jet Gun Improves Well Production in the North Sea
Authors: Scott Martin S. , Carvajal Gustavo A. , Manning Doug , Hendry Nicholas , Rogers Mike
Published: February 2011

The main focus of any perforation system is to establish effective hydraulic communication between the wellbore and the reservoir. A primary attribute for this connection is maximum penetration in the undamaged reservoir rock, especially in mature and highly depleted reservoirs. Drilling and completion fluids cause a certain amount of damage in the near well bore region, the perforating tunnels must bypass the damaged region to create the effective flow path and enable maximum well productivity. The challenge is to create a deep, clean, undamaged tunnel to maximize oil and gas production from the reservoir.

A new Triple-Jet™ perforating system was recently introduced in the North Sea, and it uses the existing shaped charges and a slightly-modified hollow steel carrier as from those currently used in the industry. This system provides a new perforating concept that exploits the beneficial aspects of firing a bank of three co-linear focused charges into the formation. The jets from the upper and lower perforating charges are angled to intersect within the formation, while the jet from the center charge is slightly delayed such that its perforating tunnel has the benefit of penetrating the tensile-stress-altered rock within the formation. The resulting shock wave from the converging jets produces a proportionally smaller crushed zone and weakened material around the perforation tunnel that is easily removed by low underbalance methods. Simulated downhole testing conditions show that this system significantly improves both penetration and flow performance and provides potentially greater well productivity than the same charges loaded in a traditional hollow steel carrier with similar charge-to- charge phasing angle. Because the Triple-Jet system produces weakened rock that is easily removed by low underbalance, it is ideal for both new well completions and re-perforating existing wells.

The new perforating technology complies with similar safety standards as conventional perforating systems, raises no additional issues with explosives licensing, guns are run and fired in the conventional manner, and does not require substantial new work or training for the crew or platform management. This paper compiles a series of laboratory experiments that are modeled with an analytical simulator and provides a brief description of the job-field application.
Comparison of Power Law and Modified Hyperbolic Decline Methods
Authors: Seshadri J. , Mattar L.
Published: February 2011

The Power Law decline analysis method has been offered as a way for predicting gas reserves in low permeability reservoirs, by matching early transient data but not over-predicting reserves as can happen when using hyperbolic decline and a high b-exponent.

This paper compares the goodness-of-fit and reserve prediction results of the Power Law versus the Modified Hyperbolic decline method; the Modified Hyperbolic being a hyperbolic decline with an imposed limit on how low the decline can become, thereby also avoiding reserve over-prediction.

Linear flow is a common occurrence in tight gas wells. For this situation, the modified hyperbolic decline (which has a direct theoretical connection) is better suited than the power law decline. Furthermore, for low values of n, Power Law appears to degenerate into hyperbolic decline.

Using synthetic and real production data, is it demonstrated that, for the most part, data matched using Power Law can also be matched using Modified Hyperbolic decline. Modified Hyperbolic decline is well understood and accepted by the industry; on the other hand, the Power Law is complex and its constituent variables are not intuitive.
Integrated Dynamic Reservoir Modeling for Multilayered Tight Gas Sand Development
Authors: Diomampo G. P. , Roach H. , Chapin M. , Ugueto G. A. , Brandon N. , Fleming C. H.
Published: February 2011

This paper summarizes the approach used for applying integrated reservoir modeling to the tight gas sands of the Pinedale Anticline in western Wyoming. The simulation of tight gas sands such as those at Pinedale has always been challenging because of the high degree of heterogeneity that needs to be retained to replicate reservoir performance, coupled with computing constraints. Added to this, simulating the Pinedale reservoir has its own unique challenges due to its characteristically thick gross sand interval composed of multiple, heterogeneous sand bodies produced commingled in a well.

An intensive data-gathering program to investigate optimum well spacing accompanied the simulation effort. A significant part of this program was the installation of pressure monitor wells1 to detect communication with surrounding producers at the hydraulic fracture stage level. This was coupled with multiple time-lapse production logs. The two data sets together allowed better definition of stage performance at producing wells.

Static models were built with fine resolution to duplicate reservoir heterogeneity. However, upscaling was necessary due to computing constraints. The upscaling procedure of Li and Beckner2 was utilized to maintain substantial geologic heterogeneity. The upscaled model was calibrated to mimic fine scale well performance prior to history matching.

Several sector upscale models were history matched using a statistical approach without compromising key aspects such as reservoir connectivity and proper mass withdrawal from each geologic sub layer. Hydraulic fractures in each stage were characterized through history matching. Given the geostatistical nature, an exact match on every frac stage and every pressure gauge located away from the producer should not be expected. Rather, a more statistical definition of a history match should be adapted to a level that still gives confidence in forecasting the value of future infill wells. The history-matched parameters were then statistically distributed to forecast more realistic future development wells.

The availability of data including pressures at observation wells and production logs was critical in narrowing the range of uncertainty in the history-matched scenarios and reduced the degree of non-uniqueness in the model thus resulting in increased confidence in model forecasts. This paper describes the methods used to overcome many of the problems encountered in modeling heterogeneous tight gas sands, such as at the Pinedale Anticline.
The Development of a New Reservoir Simulator to Model Polymer Flooding and Advanced Wells for Enhanced Heavy Oil Recovery in Bohai Bay
Authors: Zhang L. , Zhang Y. , Gong B.
Published: February 2011

Enhanced oil recovery by polymer flooding and advanced (multi-lateral) wells has been applied to develop China's offshore heavy oil reservoirs. Current commercial simulators lack the ability of modeling polymer flooding processes and multi-segment wells simultaneously, thus limits their application in making reliable production predictions and the overall development plan.

In this work, a black-oil simulator is extended to model polymer flooding by adding brine and polymer pseudo-components to the governing equation. The polymer solution, reservoir brine and the injected water are represented as miscible components of the aqueous phase. Necessary factors have been taken into account for the construction of mathematical model, such as inaccessible pore volume, polymer shear thinning effect, polymer adsorption, and relative permeability reduction factors, etc. These polymer-induced effects, modeled as nonlinear relationships, are based on lab experiments conducted upon core and PVT samples from China's heavy oil reservoirs in Bohai Bay. A fully implicit formulation is applied to solve the governing equations.

In modeling of the multi-lateral wells which are commonly applied in Bohai Bay oil fields, the multi-segment well approach is adopted. The well index (productivity index) is calculated using a 3D projection method based on Peaceman's model. This method is extended to enable its application in both structured and unstructured grid system to fully resolve complex geometrical interaction between multi-lateral wells and the reservoir. The pressure and fluid concentration distribution along wellbores is calculated through the homogeneous model, the result of which can better describe the true physics in the wellbore.

This work, for the first time, provides the development framework to model polymer flooding and advanced wells for EOR in heavy oil fields. Comparing with numerical results from commercial simulators, this model yields better accuracy and more importantly, enables the modeling of polymer flooding processes and multi-segment wells simultaneously.