bluuebunny/crossref_metadata_2025 huggingface dataset:
Mitigation of Torsional Stick-Slip Vibrations in Oil Well Drilling through PDC Bit Design: Putting Theories to the Test
Authors: Jain Jayesh R. , Ledgerwood L. W. , Hoffmann Olivier J. , Schwefe Thorsten , Fuselier Danielle M.
Published: October 2011

Stick-slip vibrations of drillstrings have been studied by researchers for several decades. The subject is gaining renewed interest as operating parameters for PDC bits have shifted to the stick-slip regime of higher bit weight and lower rotary speed for enhanced drilling performance. In Ledgerwood et al. (2010), stick-slip was identified as a primary cause of bit damage. The main objective of the current investigation is to answer the longstanding question: Do bit designs influence stick-slip behavior of the drilling system? Five prevailing industry perceptions reported in the literature are that anti-whirl bits, reduced exposure bits, and bits with bit-rock interaction number "β" > 1 are less prone to stick-slip, while highly aggressive bits and worn bits are more prone to stick-slip. Although the phenomenological basis of these theories has been provided, validation in most cases is based on anecdotal evidence from the field. Data with diagnosis based on downhole measurements in a controlled environment are scarce. Consequently, conflicting opinions continue to exist about whether any of these theories work in reality.

To assess their validity, the five leading theories were reviewed and pairs of PDC bits were designed and manufactured. Each pair consisted of a bit with a standard design and a bit that embodied one of the theories. The bits were first tested in the laboratory to characterize their response. Full-scale wells were then drilled under controlled conditions using a research drill rig in Oklahoma. In these wells, only the operating parameters were varied while BHA, formation, and other variables were unchanged for a given bit pair. The downhole vibrations were measured with a new in-bit device and an industry-proven MWD vibration monitoring service.

The most important conclusion emerging from this study is that PDC bit design has a significant effect on stick-slip vibrations. While some of the theories held true, evidence from this study did not support others. The details of test results are provided and various aspects of bit design are discussed in an attempt to enhance the understanding of stick-slip mitigation.
Impacts of the Porosity-Permeability Transform Throughout the Reservoir Modeling Workflow
Authors: Roadifer R. D. , Scheihing M. H.
Published: October 2011

Reservoir simulation history matching typically involves a process whereby reservoir rock, fluid properties and well-bore conditions are modified in some systematic way to match observed production rates and pressures. The degree to which initial reservoir and well parameters need to be modified can often be attributed to the amount and quality of hard data available and the integration of that data into the geocellular model. All too often, however, reservoir engineers find that they must modify reservoir parameters significantly in order to obtain a history match.

Historically, porosity cut-offs have often been applied to fine-grid geocellular models during upscaling to obtain the reservoir simulation-scale model. Porosity cut-offs have typically been selected by inspection of the core-derived porosity-permeability (P&P) relationship(s) and selecting the porosity that falls below an a priori specified permeability cut-off. During subsequent history matching, a disconnection between upscaled geocellular model and history-matched permeabilities becomes apparent. Permeability modifiers of two or more often need be applied across the reservoir to match reservoir performance. Discrepancies between well-log-derived porosities and core-measured porosities due to the scale (averaging) effects of the logs have been long recognized and can be accounted for in various ways (Klein et al., 2006). However, the discrepancy in permeabilities between the initial upscaled geocellular and history-matched reservoir simulation models appears to be different. In 2007, Delfiner provided a very simple, yet elegant, explanation for this discrepancy and one potential solution to the problem.

Simple examples are utilized to show how errors in the porosity-permeability transform can propagate throughout the model building and history matching process, resulting in a potentially significant underestimation of OOIP and recovery. In particular, the potential impacts of the porosity-permeability transform on net pay definition, liquid permeability, initial water saturation, relative permeability, fractional flow, production rate and ultimate recovery are discussed along with how the implementation of the suggested solution by Delfiner (2007), together with other approaches, can help mitigate these errors.
Can You Protect Your Motor Without Sacrificing Performance?
Authors: Guidroz Blair , Barton Steve , Hussain Mohammed
Published: October 2011

Achieving balance between performance and longevity of drilling motors is a constant struggle. Operating above recommended parameters delivers higher Rates of Penetration (ROP) but can be too aggressive, causing accelerated component wear and potentially, premature failure. Conservative operation decreases the component wear but can be detrimental to drilling performance. A novel approach to controlling motor performance allows operators to operate at specified limits while preventing load spikes that damage motors.

Stalling is a problem that affects bearing loading, occasionally leading to driveshaft torsional failure, but more commonly causing power section damage in the stator, reported as chunking. Chunking occurs when the elastomer in the stator has reached the fatigue limit and small pieces break free of the profile. The output performance of the power section decreases as the effective area of power section is reduced and it becomes less efficient. Reduction in output performance decreases ROP and operators will typically push motors harder to maintain ROP, further accelerating the time to failure.

An innovative internal device prevents premature failure by limiting the amount of differential pressure applied across the motor. Excess pressure is relieved by porting fluid through the center of the rotor, bypassing the power section inlet. Rotational speed decreases as flow into the power section is decreased. The pre-determined relief point is adjustable to optimize motor performance for specific applications. Preventing motor damage delivers longer drilling hours with reduced unplanned trips.

Field testing of the device has resulted in a significant reduction in motor component damage. ROP improved and was consistent through the drilling program with the controlled and steady operation of the device. Cost per foot decreased as longer intervals were drilled per motor. This device gives operators a new tool to optimize motor performance.
Optimization of Unconventional Gas Developments by Bayesian Logic and Genetic Algorithm
Authors: Willigers B. J.
Published: October 2011

Many unconventional gas developments provide only marginal economic returns. Realizing a commercial success with such projects depends on the identification of an efficient development program. Significant project value can be unlocked by, for example, optimizing the drilling program and the gas export infrastructure development. The optimization of an unconventional green-field gas development is subject to a multitude of objectives, constraints, and tradeoffs. Decision making is further complicated by multiple sources of uncertainty.

Tools like decision trees and Monte Carlo simulations can help assess exploration and early-stage development projects. However, these methods are impractical for large numbers of options and uncertainties, which are associated with many mid-stage development projects. Many decision situations are in fact complex optimization problems and practical techniques are required to enhance decision making policies.

The genetic algorithm is a powerful method to optimize complex non-linear systems for a given set of constraints. However, many real-life situations involve sequential decision making, which is likely to cause preferences to change when uncertainties are progressively resolved. The value of managerial flexibility associated with such projects cannot be quantified in a single execution of a genetic algorithm. However by a series of iterative calculations of a genetic algorithm that is conditioned with Bayesian logic the optimization procedure can be significantly improved.
Creating Portfolio Insight by a Pratical Multi-Method Optimisation Approach
Authors: Willigers B. J. , Weis F. , Majou F.
Published: October 2011

Effective portfolio management requires a comprehensive understanding of the tradeoffs between different portfolio choices. Given a set of constraints, portfolio optimisation techniques based on linear programming and genetic algorithms can be applied to identify an optimal portfolio. However, this optimal portfolio might not be the preferred portfolio. Decision makers have to understand the tradeoffs between generally conflicting objectives and constraints before one portfolio can be identified as the preferred option. Such assessment of the overall search space is not made using linear programming and genetic algorithms when used to identify a single best solution and many portfolio options will have been eliminated before an understanding of these alternatives has been developed.

Markowitz's mean-variance approach and the traditional "rank and cut" approach are typically used to establish a relationship between a portfolio's value and its variance or associated development cost. Although these methods enable decision makers to compare and contrast different options, the optimisation is limited to the portfolio value measure and a single other metric. This latter limitation is overcome by the more recently developed portfolio filtering approach. This method is practical and transparent and allows for a quick development of strategic portfolio alternatives while considering a large number of portfolio attributes. Its main drawback is that the analysed set of portfolios generally represents a subset of the total search space. Hence, as the number of feasible portfolio options increases, so does the chance that the optimal portfolio is not present in the population of sampled portfolios.

This paper presents a portfolio optimisation approach that combines linear programming, genetic algorithms and portfolio filtering. An analysis of a realistic upstream portfolio illustrates and validates the optimisation process by demonstrating how limitations of individual methods can be mitigated by combining them.
Smart Nanostructured Materials Deliver High Reliability Completion Tools for Gas Shale Fracturing
Authors: Xu Zhiyue , Agrawal Gaurav , Salinas Bobby J.
Published: October 2011

Hydraulic fracturing is considered necessary for economically efficient gas production in low natural permeability shale resources. Flow control devices such as setting balls or plugs are used for sleeve actuation or stimulation diversion during fracturing. After fracturing, these in-flowpath devices must be disposed of by methods such as drilling out or flowing back to open the flowpath for production.

Traditional low-strength ball or plug materials are prone to shape changes. Severe deformations present flowback issues and potentially require costly intervention. Additionally, it is believed that smaller balls—particularly from the well's toe section—do not always flow back to surface, leading to potential restrictions in the tubing. Operations value the concept of fully degradable ball material. Traditional degradable material, though, lacks the high material strength necessary for high-pressure fracturing and has unreliable degradation rates.

This paper will present a newly-developed nanostructured material technology called controlled electrolytic metallics (CEM), which makes high-strength and lightweight metallic composites possible. This new class of composites is completely corrodible in typical downhole environments at a predictable and controllable rate. CEM balls have passed multiple impact tests at speeds exceeding 100 mph. In 3% potassium chloride (KCl) at 200°F, these balls can completely corrode away in-situ in days. Material composition and associated processing can be changed to increase material strength by several times and the corrosion rate by several hundred times.

CEM balls performed as designed in Bakken shale field testing. Material can be designed to rapidly corrode in 5 to 15% hydrogen chloride (HCl), giving a foolproof technology with operational flexibility. The fundamentals of innovative material design and processes, along with lab test and field application data of this material will be presented. CEM-based completion tools eliminate drilling out, guarantee an open flow path for each fractured zone, and enhance well productivity. This truly interventionless technology is also being researched for high-pressure, high-temperature (HP/HT) applications.
Measurement and Modeling of Excess Oil Flow During Tertiary Gas Flood
Authors: Dehghanpour Hassan , DiCarlo David
Published: October 2011

Relative permeabilities for three-phase flow are commonly predicted from two-phase flow measurements using empirical models. These models are usually tested against available steady state data. However, the oil flow is unsteady state during various production stages such as gas injection after water flood. Accurate measurement of oil permeability (kro) during unsteady tertiary gas flood is necessary to study macroscopic oil displacement rate under micro scale events including double drainage, coalescence and reconnection, bulk flow and film drainage.

We conduct several unsteady state three-phase gravity drainage experiments with different initial conditions. We calculate kro by using the saturation data measured by a CT scanner. We find that the kro data measured during gas flooding to recover waterflood residual oil, are unexpectedly high and weakly depend on oil saturation. In contrast to steady state data, the measured kro data here are higher than the two-phase gas/oil limit. We explain how Stone I and saturation-weighted interpolation should be used to predict the permeability of mobilized oil during transient tertiary gasflood.
Catalytic Effects of Nano-Size Metal Ions in Breaking Asphaltene Molecules During Thermal Recovery of Heavy-Oil
Authors: Greff J. H. , Babadagli T.
Published: October 2011

Heavy-oil or bitumen recovery requires effective recovery of many different components of hydrocarbons for an efficient process. Production of asphaltenic components and minimizing their precipitation, which may affect the ultimate recovery and rate, is of particular interest. Conventional thermal and solvent techniques are limited in breaking asphaltene components and new types of catalysts are needed for efficient recovery of heavy-oil.

The presence of nano-size metal particles catalyzes the breaking of carbon-sulfur bonds within asphaltenes. This results in a reduction of asphaltene content, with an increase in saturates and aromatic content. The end effect of this process is a significant reduction in the viscosity of heavy oil and bitumen. Having a strong hydrogen donor present dramatically increases the amount of viscosity reduction, while not having any hydrogen donor present completely inhibits the reaction. The proper metals and corresponding concentrations need to be investigated before conducting displacement experiments in porous media.

In this paper, we investigated the effects of microwave radiation, using a standard 2.45 GHz emitter, on viscosity reduction. Different nano-sized metal particles (Fe, Fe(III) Oxide, and Cu) were used as catalysts in concentrations ranging 0.1% weight to 1% weight. Heavy oil samples were heated to and maintained at a temperature of 200°C using inductive microwave heating for a period of 5 hours. Viscosity and mass data were obtained before and after each experiment, with viscosity being measured at 55 °C, 75°C, and 95°C. Since the heavy oil samples which contained no added hydrogen donors experienced a significant vaporization of components, they must be participating in a reaction independent of the aquathermolysis reaction.
A Generic Model for Optimizing the Selection of Artificial Lift Methods for Liquid Loaded Gas Wells
Authors: Rehman A. , Soponsakulkaew N. , Bello O. , Falcone G.
Published: October 2011

An increasing number of gas wells worldwide produce at rates below their maximum potential due to liquid loading, which occurs when the gas velocity in the well falls below a critical value, at which point the liquid that was previously carried upward by the gas begins to fall back. The liquid accumulates down hole, where it increases the hydrostatic back-pressure on the reservoir, destabilizes the multiphase flow in the well, decreases gas production rate, in severe cases, can kill the well.

There are a number of tools, techniques and processes that are currently used in the industry to mitigate the impact of liquid loading. Choosing the optimum artificial lift solution for a specific occurrence of loading in the field is a very challenging task that requires an integrated, multi-disciplinary approach to deliver the highest possible value for the asset.

The objective of this paper is to develop a quantitative method which couples integrated production simulations, economic analysis and a distance-based optimization model to streamline and improve the selection of the most appropriate lifting option for given well conditions, while considering multiple factors impacting on the decision making process.

The production system is modeled with a widely available commercial software package. The feasibility of using integrated production modeling in conjunction with a distance-based optimization methodology is demonstrated with two synthetic case studies representing a high-rate and a low-rate gas well.

The results show that the proposed methodology can help optimize the selection of artificial lift solutions for liquid loaded gas wells.
A Multimodal 3D Imaging Study of Natural Gas Flow in Tight Sands
Authors: Silin Dmitriy , Kneafsey Timothy J. , Ajo-Franklin Jonathan B. , Nico Peter
Published: October 2011

Pore scale phenomena, especially in multi-phase flow, have a strong impact on the mechanisms and efficiency of gas recovery. We studied the impact of the pore space geometry on single- and two-phase flow properties of tight-sands. X-ray computed tomography (CT) and scanning-electron microscopy (SEM), along with other imaging tools provide insights into pore structure at multiple scales. Segmented micron-scale resolution CT 3D images were used as input data for simulations based on the Maximal Inscribes Spheres (MIS) method. Finite-difference flow simulations of creeping flow on MIS-evaluated equilibrium fluid distribution predict of the relative permeability curves as functions of saturation. A pore-scale model of two-phase gas flow accounts for condensate dropout based on thermodynamic equilibrium. The pore-scale analysis results are applied in optimal-control model of wet gas flow with liquid skin.

This study leads to the following conclusions: (a) the estimated minimal wetting fluid threshold saturation, at which the gas phase is disconnected, is much lower than that for conventional sandstones; (b) pore-scale flow simulations suggest that in imbibition, the gas and brine (or other wetting fluid) can block the other phase's flow ("Permeability Jail"), where the blockage of gas is of capillary nature, and the blockage of liquid phase is dynamic; (c) pore-scale simulations of drainage do not show mutual blockage of the fluids; (d) the rate of the local condensate dropout is proportional to the dot product of the local flow velocity and pressure gradient; (e) upscaling of conclusion (d) to Darcy scale leads to condensate dropout rate proportional to the pressure gradient; (f) the optimal-control model suggests that gas well production-rate control may have potential for considerably increasing the total gas recovery.
Conversion of Cyclic Steam Injection to Continous Steam Injection
Authors: Alikhlalov K. , Dindoruk B.
Published: October 2011

Estimated total world in-place oil volumes are between 9 trillion and 13 trillion barrels, of which 30% is conventional crude. The rest is 30% oil sands and bitumen, 25% is "extra heavy" oil and 15% is "heavy" oil. Normally definition of heavy oil is based on gas free properties of the oil. An oil is classified as heavy oil if the dead oil viscosities are between 100 centipoises to 10000 cp at reservoir temperatures with API's between 10 to 20. Extra-heavy oil is commonly defined as oil having a gravity of less than 10° and a reservoir viscosity more than 10 000 centipoises. When reservoir viscosity measurements are not available, extra-heavy oil is considered to have a lower limit of 4° API (WPC Report - 2007). Though industry has known about heavy oils for a century, it still provides a minute fraction of the world's production. Because in many cases oil will not flow at economical rates (mainly due to high viscosities). One of the most important technical challenges for Enhanced Oil Recovery (EOR) engineers is to develop an economical and feasible recovery process for heavy oil reservoirs.

Depending on the reservoir-fluid system, commercial rates can be achieved by injecting (heat) steam. However, injectivity can be one of the key factors that can lead to difficulties to deliver enough heat to contact significant portion of the reservoir with steam (or for any other potential injectant). The main reason for such low injectivities in targeted heavy oil reservoirs originates from the excessively high in-situ oil viscosities. In order to facilitate the injection of reasonable quantities of steam in a continuous manner, cyclic steam injection techniques are often utilized at early stages of such projects, especially for extra heavy oil reservoirs. From the full project time cycle point of view, a combination of cyclic and continuous steam injection could be used to overcome this problem. In this paper, we have considered a five-spot pattern and studied optimum time for the conversion of cyclic steam injection to continuous steam injection for various type of reservoir and fluid properties using a commercial numerical simulator (STARS, 2009). To our knowledge, this is the first study that addresses the cyclic to contuinuous steam injection conversion time and correlates it to simple measurable quantities for the benchmark system with the reservoir/fluid properties selected.
Combined Temperature and Pressure Data Interpretation: Applications to Characterization of Near-Wellbore Reservoir Structures
Authors: Duru Obinna O. , Horne Roland N.
Published: October 2011

The models that describe distributed temperature behavior in a reservoir appear as advection-diffusion equations with forcing terms that include compressibility effects due to Joule-Thomson and adiabatic expansion. The model lends itself to solution techniques like Operator Splitting which decomposes a multiphysics, multiscale problem into components representing different simple physics and scales, where each component can be solved independently at each time step using any appropriate technique for the physical process.

Unlike diffusion, advection does not destroy information and it is nonsmoothing and preserves sharp boundaries. By Method of Characteristics (MOC), a process can be estimated as it is advected downstream, from an initial data line, along characteristic paths at some characteristic velocity. This idea has useful implications on what information is carried by the advection processes that occur in a reservoir, such as heat advection.

In this paper, the results of solving the temperature model by Operator Splitting are presented. This approach utilizes the fact that temperature signatures, generated by spatial pressure changes in the reservoir due to Joule-Thomson and adiabatic expansion effects, are transported downstream in time from the initial line of generation to the wells. Along the corresponding characteristic curves, this transport is described by the characteristic velocity, and time to reach the well. Importantly these curves are independent of the pressure model but are dependent on the convective thermal velocity. The result is that reservoir structures that generate significant spatial pressure changes produce temperature signatures that are transported along the characteristic solution lines from the point of generation to the wells. Back calculations using the arrival times and and corresponding velocities give the location of the reservoir structures.

This technique was applied to the calculation of damaged radius, stimulated radius and inner boundaries of a multiring reservoir system, using temperature measurements and showed that near wellbore properties that are masked by wellbore storage in pressure transient analysis can be revealed by the slower moving temperature field. A proposal for new well test design to utilize this approach is also presented.
Gel Flooding Pilot Test and Evaluation Method Studies to Control Water Channeling in Conventional Heavy Oil Reservoir of Bohai Bay
Authors: Li Yanlai , Su Yanchun , Ma Kuiqian , Li Qizheng , Jia Xiaofei
Published: October 2011

LD oilfield was put online in Bohai Bay of China in 2005, characterized by huge thickness, high permeability, severe heterogeneity and high crude oil viscosity(210~460cp).Water injection in this oilfield was initiated in 2007. There are many challenges during water injection because high oil-water viscosity ratio leads quick breakthrough of injecting water, and high increasing rate of water cut, and so on.

In order to solve these problems, the gel flooding pilot test was conducted in LD oil field during the year 2009 to 2010. Before pilot test, laboratory study under field conditions was conducted to determine the chemical parameters of the gel injection. We also did numerical simulation study with CMG STARS. A range of variation of critical parameters was evaluated in the simulation for understanding the gelation process in the reservoir. The model was used to predict the reservoir response under different gel chemical parameters. Results from simulation showed that water cut reduced from 15.9 to 36.6% which matched the trends observed in wells. On other hand, dynamic method is also used to evaluate the gel pilot test. The Hall curve analysis was used to evaluate the effectiveness of the injection well and to calculate the resistance factor(RF) & residual resistance factor (RRF) (RF from 4.11 to 6.88, and RRF from 3.18 to 7.97 in LD oilfield). The decline curve analysis was used to obtain net incremental oil by gel injection treatment.

Results from two well patterns conducted gel pilot test in 2009 indicate that water cut reduction ranged from 3.2 to 36.8% and average oil production increases 14.7 m3/d. Based on results, another pilot test with two new well patterns were conducted in 2010 and we are now evaluating the new pilot test.

The pilot test & evaluation technology provides the foundation for promoting application of techniques to stabilize oil rate and control water production in reservoirs with conventional heavy oil in Bohai Bay of China.
Advanced Workflows For Joint Modelling Of Sedimentary Facies And Diagenetic Overprint, Impact On Reservoir Quality
Authors: Doligez B. , Hamon Y. , Barbier M. , Nader F. , Lerat O. , Beucher H.
Published: October 2011

The relationships between sedimentological facies and diagenetic properties differ depending on burial and geological history. In this paper we propose several examples where different quantitative expressions of diagenetic imprints lead to different workflows to be applied, to obtain final simulations reproducing both the sedimentary facies and the diagenetic trends in reservoir models.

A first case is based on an outcrop study of mixed siliciclastic-carbonate facies. The relationships between sedimentary facies and diagenesis have been used to define truncation rules for the plurigaussian algorithm, which aims at simulating both the distribution of sedimentary facies and the diagenetic overprint. Another workflow has been developed on this example, using the bi-plurigaussian simulation algorithm to address the problem of heterotopic bivariate conditional simulation (the two variables are known at different locations).

A second example is related to early diagenesis characterization. In this example (Madison Formation, Wyoming, USA), diagenetic imprints have been quantified, corresponding to a succession of diagenetic phases (micritization, calcite cementation, dolomitization...), that can coexist in the same sedimentary facies. The workflow using plurigaussian and nested simulation algorithms shows the impact of such joint simulations, as the diagenesis may completely modify the distribution of reservoir properties only based on a facies simulation.

In a third example, the modeled Aptian/Albian formation includes hydrothermal dolomites (HDT) associated to fractures and faults hosted in reefal and slope limestones. Simulations succeed in redistributing the HTD correctly at the surface and in the subsurface. Hence, in the deeper parts of the Aptian/Albian reefal rock unit, the dolomite is inherently associated to fractures, while at shallower levels, dolomitization seems to be more lateral, affecting probably more permeable facies. These results provide insights and numerical means for estimating volumes of dolomites (vertically and laterally) in an excellent case study of fracture-related HTD.

Diagenesis alters the original relationships between depositional facies and petrophysical properties in a reservoir. The quantitative integration of sedimentological facies and diagenetic properties is a key point to obtain a realistic geological model in reservoir studies.
The Design and Application Of Latest Generation Inflow Control Devices In Non-Horizontal Wells in the Bhagyam Field, India
Authors: McKenzie Tim , Wenk Andrew , Chavan Chetan , Kumar Sanjay , Khan Parvez , Garcia Gonzalo
Published: October 2011

Bhagyam is the second largest oilfield discovered to date in the Barmer Basin, India with more than 400mmb of viscous, waxy crude in place. This paper describes the evaluation, design and selection process for the use of the latest generation ICD in non-horizontal wells.

Sand face completions comprise sand screens coupled with an ICD. Inflow control was highly desirable due to the oil viscosity variation, high permeability, heterogeneity and adverse mobility ratio and the fact the completions could not be easily accessed below a PCP. Oil viscosity ranges from 14 to 250cp varying with depth. The variation in reservoir thickness, produced fluid viscosity and well productivity required a field adjustable pressure drop capability in the ICD. The ICD had to perform at high viscosity and needed to be tolerant to wax and sand production. The operator's experience in nearby fields observed the benefits of ICDs for providing efficient sand face cleanup in horizontal wells. It was vital to model this system accurately however there were significant challenges as no previous examples of using these devices in non-horizontal wells could be found and the ICD completion had not been modeled in a dynamic simulator for this scale of field development.

A dynamic simulation model which included the ICD completion was used to evaluate various completion options. A significant amount of work was performed to ensure the ICD was accurately modeled in the simulator. The simulations showed a long term benefit from using the ICD. To date 23 production wells have been drilled and of these 16 have been completed with the ICD screen systems.

This is one of the first applications of the latest generation ICD in non-horizontal wells particularly on a full field scale. It is also a case study of modeling the ICD completion with a dynamic simulator.
A New Approach to Deepwater Drilling Data Analysis Offers Enhanced Real Time Capabilities in a Post Macondo World
Authors: Greve John F.
Published: October 2011

Deepwater drilling activity in the Gulf of Mexico is no longer a given in the aftermath of the BP Macondo blowout. The new and ever evolving process to apply for drilling permits and operate now greatly depends on:

Optimal well designs certified for accuracy by Professional Engineers Thorough real-time monitoring of pertinent surface and down-hole data, and Deployment of new joint industry well capping and spill containment equipment for response to a blowout.

This paper makes no attempt to address the topics in items 1 and 3. In regard to item 2, a new method for loading and analyzing live time and depth data has shown merit during recent 2010 trials on two deepwater wells, one offshore eastern Canada and the other offshore west of the Shetland Islands. Rapid data access and standardized visualization of high resolution time, depth, and survey data is vital to insure that the occasional well control event doesn't become today's worldwide news headline. Deepwater drilling management demands a highly trained staff with timely access to data in a format easily used by the key decision makers wherever they are.

After the BP Macondo blowout, the news frenzy and blame game quickly showed the entire world that all operators may not be truly partnered with their rig and service suppliers in cooperative efforts to safely drill and complete the high rate wells which have historically made the deepwater Gulf of Mexico an attractive area to explore. After the blowout, the gathering of high quality data from remote real time data centers was quickly elevated to critical status for use in the government's investigation. High quality data collection and interpretation should always be managed with utmost attention to detail in light of the inherent risks of deepwater drilling and the fact that the industry simply cannot afford another incident.

After a major disaster in any business sector, new technology is always promoted as a key ingredient to avoid and manage any future accident. The oil industry must now meet the challenge of proving to the regulators charged with enforcement that our organizations have the capability for creating exacting pre-drill well plans, managing and prudently using real-time information. and responsibly responding to any well control event up to and including a blowout.
Statoil Experiences and Consequences Related to Continuous Chemical Injection
Authors: Olsen John Helge
Published: October 2011

Current completion solutions using Continuously Chemical Injection system faces challenges to prevent plugging of the capillary line. Where as Completion engineering principles have in the past mainly focused on the physical properties of the injection valve and mandrel, the chemists focus have been finding effective chemicals. We now experience that we need to have a system focus. The Chemical Injection Systems are not covered by any industry standards such as ISO or API, some elements are covered but none with focus on the entire system. As such Statoil has experienced that there are many other aspects and challenges linked to Chemical Injection systems that has not been explored in the past, and as a consequence Statoil has initiated an enhanced program to gain more knowledge and experience to better understand the physical and practical interlinks related to Continuous Chemical Injection.

Understanding the behaviour of chemicals in vacuum or near-vacuum pressure regimes in the upper part of the capillary line is one of the keys to understand the challenges related to these completions. Through communication with other operators throughout our industry, we understand that the challenges we have experienced are also relevant for others well operations. Statoil believe in an open environment where experiences are shared within the industry to improve our and others operations and to develop more robust solutions for the future.
Computational Analysis of Stress Interference Effect for Hydraulic Fracturing in Waste Injection Wells
Authors: Yao Yao , Lewandowski Jerome , Ellison Tim , Searles Kevin
Published: October 2011

Hydraulic fracturing is a key mechanism for injection into waste disposal wells. To successfully inject drill cuttings slurry or produced water under fracturing conditions and prevent unwanted migration, it is essential to predict the extent of hydraulic fractures accurately based on understanding the fundamental fracture mechanisms. Popular hydraulic fracture models for injection wells continue to rely on pseudo-3D fracture technology. However, when injection takes place in multiple, closely spaced wells, or under the influence of offset producers, stress interference effect on fracture geometry can hardly be predicted based on simple single-well methods. If the distance between the multiple injection wells is small such that pronounced stress perturbations exist, the stress interference could influence the fracture geometry and orientation. This paper presents a study on the stress interference effects on fracture orientation and spatial extent caused by multiple injection wells using a hybrid computational method incorporating finite element and boundary element fracture models. To investigate the stress interference effects, a pore pressure cohesive zone model was developed to predict hydraulic fracturing for injection wells through finite element analysis and sub-modeling technology. The model was applied to investigate the stress perturbation effect on fracture geometry caused by long-term, high-rate, multi-well waste injection into a heterogeneous geological environment. Boundary element analysis was performed to simulate the possible fracture reorientation and fracture merging caused by the changing of the stress field with the propagation of multiple hydraulic fractures. Injection wells with different well distances and stress boundary conditions were investigated. A 3D analytical tool has been developed to simulate the changes of stress due to the depletion in pore pressure from an offset location. The computational analysis on the stress field was verified with the analytical solution. Based on the finite element and boundary element analyses, revised stresses were incorporated into the tuned pseudo-3D models to update the hydraulic fracturing prediction to account for stress interference effects. Ultimately, the fracture predictions were quantified under the influence of stress interference.
Experimental Investigation of Three-Phase Gas-Oil-Water Slug Flow Evolution in Hilly-Terrain Pipelines
Authors: Ersoy G. , Sarica C. , Al-Safran E. M. , Zhang H.-Q.
Published: October 2011

A hilly-terrain pipeline consists of horizontal, upward inclined and downward inclined sections. The lack of understanding of how three-phase slug flow characteristics change in hilly-terrain pipelines may lead to inaccurate modeling of the phenomenon and thus poor pipeline and downstream facility designs. Although several slug tracking models are available, their performance has not been thoroughly tested against gas-oil-water data in hilly-terrain pipelines due to the scarcity of such data.

Three-phase gas-oil-water slug flow evolution in hilly-terrain pipelines was studied experimentally. The constructed experimental facility was a 69-m long, 50.8-mm ID outdoor facility with ±5° inclination angle for a valley configuration. Three-phase slug flow developments in the hilly-terrain section were observed and analyzed with the measured pressure drop, average liquid holdup, phase distributions and slug characteristics. This study improves the current understanding of gas-oil-water flow behavior in hilly-terrain pipelines and the effect of water cut on slug flow characteristics.

This understanding will improve the existing slug tracking models or can be used to develop new models when, necessary, for the proper design and safe operation of three-phase pipeline systems. Seven three-phase slug flow patterns were identified based on oil-water mixture in the upstream horizontal section of the hilly-terrain unit. These flow patterns were analyzed and compared with slug dissipation in the downhill section of the hilly-terrain unit. When these flow patterns were compared with two-phase slug dissipation behavior, no water cut effect was observed. For moderate and high flow rates, slugs with different oil-water mixing status had differences in slug frequencies and lengths. However, the evolution of liquid slug length distributions for 20% and 80% water cuts in the upstream horizontal section and upward inclined section did not show any significant dependence on water cut.
The Use of Attenuation and Phase Shift to Estimate Permeability Distributions from Pulse Tests
Authors: Ahn Sanghui , Horne Roland N.
Published: October 2011

In this work, attenuation and phase shift information acquired from pressure pulse tests at multiple frequencies was used to estimate the permeability distribution of reservoirs. By preprocessing the time series pressure data at the active well and the observation well, not only are the sizes of both the time and frequency conditioning data reduced tremendously, but also there is no need to know the flow rate. However, to put this method into practice and to know its limits, an investigation was conducted under various reservoir conditions to resolve the issues of detrending (removing transient upward trends in the pressure data) and to develop the Fourier transform procedures that are necessarily involved with this approach.

In addition to estimate horizontal heterogeneous permeability from a radial multicomposite reservoir, the method utilizing multiple frequency attenuation and phase shift information was applied to a partially penetrating well in a multilayered reservoir with crossflow to reveal the heterogeneous vertical permeability distribution.

The performance of the frequency method was investigated in comparison to straightforward pressure history matching. Quasi-Newton line-search optimization with gradient information was used for both methods. In addition, we investigated the sensitivity of the permeability estimation to perturbation in both pressure data and attenuation and phase shift information.

A heuristic method for detrending was devised which helps in obtaining accurate attenuation and phase shift information. Cases with different values of storage, skin, and boundary conditions were considered. The impact of varying the number of periods and the sampling rate were checked to determine the sensitivity of Fourier transformation.
Improved Understanding of Reservoir Connectivity in an Evolving Waterflood with Surveillance Data
Authors: Parekh B. , Kabir C. S.
Published: October 2011

Establishing connectivity among various injectors and producers is a key to improving the understanding of a reservoir under waterflood. This understanding improves the estimates for ultimate recovery and also helps to better define the future development plan. In deepwater turbidite reservoirs, numerical flow-simulation models are used to make performance predictions, with reservoir connectivity as one of the key uncertainties.

In the initial phase of field development, interwell tracers were used to assess the connectivity. As more wells were drilled, updates were required for the simulation models. Instead of waiting for the next phase of an ongoing tracer program, both rate-transient analysis (RTA) and capacitance-resistance model (CRM) were used to understand connectivity. The input for both RTA and CRM are the rates and pressures, which are being gathered with real-time surveillance.

This paper presents a case study to compare findings from the use of interwell tracer data with the results of CRM based on dynamic data. Another study element demonstrates the use of RTA in identifying and estimating the volume of thief zone. Attempts are made to use CRM and RTA to predict connectivity based on performance prior to experiencing water breakthrough.

These case studies demonstrate the application of RTA and CRM in ongoing waterfloods. The CRM concurred with the initial tracer results and helped to understand the change in pressure distribution with time as the field was being developed. We learned that the use of CRM can be a viable alternative to an interwell tracer program to reduce uncertainty related to injector-producer connectivity. CRM also helped in understanding the efficiency of the injectors, which is important in a facility with limited water injection capacity. The ease of use of CRM and RTA makes them useful as screening tools in the process of developing a detailed flow-simulation model.
Stand Research and Analysis of Liquid-Gas Jet-Pump's Operation Characteristics for Oil and Gas Production
Authors: Drozdov A. N. , Malyavko E. A. , Alekseev Y. L. , Shashel O. V.
Published: October 2011

Liquid-gas ejector is a hydraulic machine, in which the energy exchange of active fluid (liquid) and passive fluid (gas) occurs through their direct mixing. Bench research have been carried out, in which the active fluid was injected in the nozzle of LGE, a pressure of active and passive fluids, and an output pressure at different geometrical parameters (such as nozzle diameter, the diameter and length of the mixing chamber) were controlled, pressure and power characteristics were constructed and analyzed. The stand consists of a submersible multistage centrifugal pump, ejector, tank and separator. Laboratory stand has unique capabilities and provides a power pressure in the nozzle of the ejector up to 20 MPa, and an intake pressure (in the suction chamber) - up to 5 MPa. This stand is fully simulates the use of an ejector in well's and field conditions.

The use of liquid-gas ejector enables applying the technologies of water-alternating gas impact on the layer, hydro-jet method of operating wells, tandem technology of the jet device and ESP in the well. Also, the use of LGE enables to utilize associated gas by injection it into the reservoir (implementing the method of enhanced oil recovery) or in the pipeline for its transportation without flaring.

The main results are the characteristics of LGE with high efficiency in various operating conditions. The region of operation parameters of the ejector, where the highest efficiency values were achieved, was established.

LGE are easy to use, they have small overall dimensions and weight, they are able to transport corrosive fluids and to reach high efficiency; and the problem of utilization of associated gas can be solved using them. They could compete with expensive compressors, multi-phase pumps and booster units.