bluuebunny/crossref_metadata_2025 huggingface dataset:
Sand on Demand: A Laboratory Investigation on Improving Productivity in Horizontal Wells Under Heavy-Oil Primary Production—Part II
Authors: Meza-Díaz Brigida , Sawatzky Ron , Kuru Ergun
Published: November 2012

The cold-production-recovery process, also known as cold heavy-oil production with sand (CHOPS), is a method for enhancing primary heavy-oil production by aggressively producing sand. It is successful in vertical (or slanted or deviated) wells in western Canada. In this process, large amounts of sand are produced on a continuing basis along with heavy oil. Attempts at cold production in horizontal wells have not been particularly successful. When sand production has been generated in horizontal wells, these wells have tended to become plugged with sand.

This paper presents the results of experiments performed to assess the feasibility of applying cold heavy-oil production in horizontal wells that have been completed with slotted liners using less-aggressive (i.e., managed) sand-production strategies. Specifically, the effects of slot size, confining stress, fluid velocity, and sand-grain sorting on sand production were investigated.

The results indicate that slot-size selection is critical for establishing "sand on demand." From the experiments, a correlation between slot size and controlled sand production was found for well-sorted sands. This correlation should allow for the specification of appropriate slot sizes for target reservoirs containing well-sorted sands.

In the experiments, when flow rates resulted in low but persistent sand production, channels and/or elliptical dilated zones were created that greatly enhanced the effective permeability near the slot. This observation suggests that producing at low and steady sand cuts for a long period of time might bring two benefits: a way to transport the sand out of the well without causing plugging and the creation of high-permeability channels or zones that can improve production from the reservoir.

To summarize, if the appropriate slot size were combined with the right drawdown rates, controlled sand production could be achieved, with attendant significant increases in permeability. This suggests that substantially increased oil-production rates could be achieved from horizontal wells if sand-production rates could be maintained at low but persistent levels.
An Improved Adjoint-Sensitivity Computation for Multiphase Flow Using Wavelets
Authors: Awotunde A.A.. A. , Horne R.N.. N.
Published: November 2012

In history matching, one of the challenges in the use of gradient-based Newton algorithms (e.g., Gauss-Newton and Leven-berg-Marquardt) in solving the inverse problem is the huge cost associated with the computation of the sensitivity matrix. Although the Newton type of algorithm gives faster convergence than most other gradient-based inverse solution algorithms, its use is limited to small- and medium-scale problems in which the sensitivity coefficients are easily and quickly computed. Modelers often use less-efficient algorithms (e.g., conjugate-gradient and quasi-Newton) to model large-scale problems because these algorithms avoid the direct computation of sensitivity coefficients. To find a direction of descent, such algorithms often use less-precise curvature information that would be contained in the gradient of the objective function. Using a sensitivity matrix gives more-complete information about the curvature of the function; however, this comes with a significant computational cost for large-scale problems.

An improved adjoint-sensitivity computation is presented for time-dependent partial-differential equations describing multiphase flow in hydrocarbon reservoirs. The method combines the wavelet parameterization of data space with adjoint-sensitivity formulation to reduce the cost of computing sensitivities. This reduction in cost is achieved by reducing the size of the linear system of equations that are typically solved to obtain the sensitivities. This cost-saving technique makes solving an inverse problem with algorithms (e.g., Levenberg-Marquardt and Gauss-Newton) viable for large multiphase-flow history-matching problems. The effectiveness of this approach is demonstrated for two numerical examples involving multiphase flow in a reservoir with several production and injection wells.
Casing While Drilling (CwD): A New Approach To Drilling Fiqa Formation in the Sultanate of Oman—A Success Story
Authors: Sánchez F.. , Houqani S.. , Turki M.. , Cruz M..
Published: November 2012

Highly reactive Fiqa shale used to compel well engineers in the Sultanate of Oman to plan drilling phase of surface and intermediate sections primarily based on time exposure to aqueous drilling fluid water-based mud (WBM). The new approach of drilling the time-dependent Fiqa formation using casing-while-drilling (CwD) allows well engineers to plan prospective top/intermediate wellbore sections differently by enhancing the overall drilling performance. This reduces the risk of setting casing strings at unplanned depths, getting pipe stuck, or reaming continuously when drilling with conventional drillstring. The technical feasibility study, risk assessment, planning, execution, and the lessons learned during the process of drilling two top-section pilot projects are described in this document. The CwD team compares the drilling performance of several offset wells and suggests actions to improve the CwD technology in Oman.

Two 17½ - and 22-in. surface sections were drilled successfully with large-diameter casing strings and reached 754- and 894-m measured depths, respectively. The implementation of the CwD concept reduced the overall drill/case phase time up to 40%, in comparison with the average using conventional drilling in those fields. Exposure time of Fiqa to aqueous environment was reduced by eliminating conditioning trips and nonproductive-time (NPT) associated with wellbore instability. Drilling both sections with non-retrievable 17½×13⅜-in. and 22×18⅝ -in. CwD systems did not require modification of well design or rig. The optimization of this technology will support its implementation as the conventional drilling approach in some fields in Oman.
Injection Profiling During Limited-Entry Fracturing Using Distributed-Temperature-Sensor Data
Authors: Hoang Hai , Mahadevan Jagannathan , Lopez Henry
Published: November 2012

Tight gas plays often have multiple lenses of producing formations. Multizone fracturing or limited-entry fracturing is a cost-effective method to complete and produce tight gas wells in these layered reservoirs. The rate and volume of fracturing fluid injected into the different layers have an important role in determining the fracture characteristics. However, because of the spatial restriction of downhole conditions, it is very challenging to obtain a specific injection rate for each perforated zone. Temperature variations in the wellbore, outside of the casing, are available with new technology such as distributed-temperaturesensor (DTS) fiber-optic cables. The main objective of this study is to relate the wellbore-temperature changes as measured by DTS data to the wellbore and fractured-interval injection rates during a multizone fracturing process.

We develop a forward simulation model on the basis of mass and energy conservation for calculating the temperature profile and temperature history in the wellbore and in the rock surrounding the wellbore. The model allows for liquid flow into the fractured interval. Subsequently, the model is integrated with an inverse-estimation algorithm, which is used to estimate flow rates both in the wellbore and into the fractured interval. The estimation algorithm is based on a gradient search method. A distinguishing feature of this work is the development of a radial model used to represent the temperature evolution in the near-wellbore region. The higher order allows accurate calculation of the temperature in the wellbore while still capturing the fluid-flow and heat-transport aspects of the hydraulic-fracture propagation.

Our estimation results show a good comparison between the calculated temperature profiles and those observed in the field with DTS. Also, the model is able to estimate a flow-rate history consistent with total field-injection volume. This work enables an accurate and quick interpretation of the wellbore DTS data to determine the interval injection rates during a hydraulic-fracturing process. Knowledge of accurate interval injection rates and the corresponding fracture characteristics can be useful in designing a better limited-entry completion that can optimize the fracture length by use of rate control and/or fluid diversion.
Robust Constrained Optimization of Short- and Long-Term Net Present Value for Closed-Loop Reservoir Management
Authors: Chen C. , Li G. , Reynolds A. C.
Published: November 2012

In this paper, we develop an efficient algorithm for production optimization under linear and nonlinear constraints and an uncertain reservoir description. The linear and nonlinear constraints are incorporated into the objective function using the augmented Lagrangian method, and the bound constraints are enforced using a gradient-projection trust-region method. Robust long-term optimization maximizes the expected life-cycle net present value (NPV) over a set of geological models, which represent the uncertainty in reservoir description. Because the life-cycle optimal controls may be in conflict with the operator's objective of maximizing short-time production, the method is adapted to maximize the expectation of short-term NPV over the next 1 or 2 years subject to the constraint that the life-cycle NPV will not be substantially decreased. The technique is applied to synthetic reservoir problems to demonstrate its efficiency and robustness. Experiments show that the field cannot always achieve the optimal NPV using the optimal well controls obtained on the basis of a single but uncertain reservoir model, whereas the application of robust optimization reduces this risk significantly. Experimental results also show that robust sequential optimization on each short-term period is not able to achieve an expected life-cycle NPV as high as that obtained with robust long-term optimization.
A Multiscale Workflow for History Matching in Structured and Unstructured Grid Geometries
Authors: Bhark E.. , Rey A.. , Datta-Gupta A.. , Jafarpour B..
Published: November 2012

We present the development and field application of a workflow for multiscale reservoir-model calibration that seamlessly integrates production data into the reservoir description from the facies to the grid-cell scale. To start with, the permeability field is parameterized using a novel grid-connectivity-based transformation basis that can be applied with any model geometry, including unstructured and corner-point grids. The parameterization basis functions emerge from spectral decomposition of the grid-connectivity Laplacian and are related to the structural harmonics of the grid. To reconcile data with model resolution during history matching, we first use the coarsest-scale basis functions to identify the large-scale variability. Additional smaller-scale basis elements are then adaptively incorporated to successively refine the model to a level supported by data resolution. During refinement, the inclusion of more detailed basis functions into the parameterization is determined by generic modal frequency when the prior model is unavailable or by using prior information when available. In the final step of the workflow, a streamline-based inversion is performed to locally adjust the reservoir model at grid-cell resolution along preferential-flow paths defined during the coarser-scale parameterization.

We demonstrate the suitability and effectiveness of the developed workflow through application to an offshore turbidite reservoir with frequent well intervention, including shut-ins and recompletions. The static model has over 300,000 cells, a complex channelized interpretation with faults, four injector/producer pairs with deviated wells, and over eight years of production history, including water cut and pressure data. The grid-connectivity-based parameterization effectively updates the prior regional permeability at scales and in locations warranted by the data, while preserving the geologic continuity and avoiding ad hoc redefinition of regions given the sparse well pattern. The multiscale calibrated-permeability field indicates flow communication previously unrecognized in static geologic interpretation or manual history matching.
Development of a Transient Mechanistic Two-Phase Flow Model for Wellbores
Authors: Shirdel Mahdy , Sepehrnoori Kamy
Published: November 2012

A great deal of research has been focused on transient two-phase flow in wellbores. However, there is lack of a comprehensive two-fluid model in the literature. In this paper, we present an implementation of a pseudo-compositional, thermal, fully implicit, transient two-fluid model for two-phase flow in wellbores. In this model, we solve gas/liquid mass balance, gas/liquid momentum balance, and two-phase energy balance equations to obtain five primary variables: liquid velocity, gas velocity, pressure, holdup, and temperature. This simulator can be used as a stand-alone code or can be used in conjunction with a reservoir simulator to mimic wellbore/reservoir dynamic interactions. In our model, we consider stratified, bubbly, intermittent, and annular flow regimes using appropriate closure relations for interphase and wall-shear stress terms in the momentum equations. In our simulation, we found that the interphase and wall-shear stress terms for different flow regimes can significantly affect the model's results. In addition, the interphase momentum transfer terms mainly influence the holdup value.

The outcome of this research leads to a more accurate simulation of multiphase flow in the wellbore and pipes, which can be applied to the surface facility design, well-performance optimization, and wellbore damage estimation.
A New Analytical Method for Analyzing Linear Flow in Tight/Shale Gas Reservoirs: Constant-Flowing-Pressure Boundary Condition
Authors: Nobakht Morteza , Clarkson C.R.. R.
Published: November 2012

Many tight/shale gas wells exhibit linear flow, which can last for several years. Linear flow can be analyzed using a square-root-of-time plot, a plot of rate-normalized pressure vs. the square root of time. Linear flow appears as a straight line on this plot, and the slope of this line can be used to calculate the product of fracture half-length and the square root of permeability.

In this paper, linear flow from a fractured well in a tight/shale gas reservoir under a constant-flowing-pressure constraint is studied. It is shown that the slope of the square-root-of-time plot results in an overestimation of fracture half-length, if permeability is known. The degree of this overestimation is influenced by initial pressure, flowing pressure, and formation compressibility. An analytical method is presented to correct the slope of the square-root-of-time plot to improve the overestimation of fracture halflength. The method is validated using a number of numerically simulated cases. As expected, the square-root-of-time plots for these simulated cases appear as a straight line during linear flow for constant flowing pressure. It is found that the newly developed analytical method results in a more reliable estimate of fracture half-length, if permeability is known. Our approach, which is fully analytical, results in an improvement in linear-flow analysis over previously presented methods. Finally, the application of this method to multifractured horizontal wells is discussed and the method is applied to three field examples.
Acidizing-Induced Damage in Sandstone Injector Wells: Laboratory Testing and a Case History
Authors: Al-Mohammad A.M.. M. , Alkhaldi M.H.. H. , Al-Mutairi S.H.. H. , Al-Zahrani A.A.. A.
Published: November 2012

Throughout a well's lifetime, formation damage can occur during the activities of drilling, completion, injection, or well-stimulation treatments. Typically, remedial treatments to restore the well performance involve injection of reactive fluids capable of removing such damage. Therefore, understanding damage mechanism and type is critical for fluid selection and effective treatment design. Without this knowledge, the conducted stimulation treatment could cause a more-severe form of formation damage.

This report discusses the improper use of mud acid [at 9 wt% hydrochloric acid (HCl)/1 wt% hydrofluoric acid (HF)] in restoring the injectivity of Well N-510. The subject well was stimulated with two acid-stimulation treatments in an attempt to improve the poor results of a previous cleanout job, conducted to remove mud filter cake. These treatments were designed to remove the damage that has been limiting the well injectivity. However, it was found that these acidizing treatments created a new formation damage that resulted in the severe decline of well injectivity.

Integration of chemical-analysis techniques performed on return fluids and coreflood experiments was used to assess the effectiveness of all conducted treatments. This report demonstrates the techniques used to identify the source and type of formation-damage mechanism that occurred during each treatment. On the basis of these studies, it was found that the poor results of the cleanout job were caused by precipitation of calcium sulfate. This precipitation was a result of the mixing between spent cleanout acid, having a high amount of calcium, and the high-sulfate-content water. Most of this precipitation occurred in the wellbore vicinity during the preceding stages of the well flowback.

Calcium sulfate precipitation had a negative impact on the performance of the conducted acid-stimulation treatments. In the presence of this precipitation, the two successive mud-acid-stimulation treatments created another form of damage (i.e., in-situ fluoride-based scale). Initially, the fresh injected mud acid dissolved most of the calcium sulfate scale, and as a result, it contained a high amount of dissolved calcium ions. However, upon the spending of injected mud acid in the formation, calcium fluoride precipitated as a result of the increase of solution pH value.

The interactions between different acid systems and the constituents of the downhole environment, resulting in the precipitation of calcium sulfate and calcium fluoride, are discussed. In addition, this report provides recommended modifications for future stimulation treatments, conducted under similar conditions, so as to prevent the formation of these scales.
Integrating Mini-DST-Derived Permeability With Other Sources: A Case Study
Authors: Harmawan I.. , Kabir C.S.. S. , Habib S.. , Kennedy J.. , Henson J.. , Minhas H..
Published: November 2012

Permeability is the cornerstone of any reservoir-flow modeling that leads to field development and production management. Typical sources of permeability include cores, logs, wireline formation tests [or minidrillstem tests (mini-DSTs)], and conventional DSTs. However, integrating various sources of permeability at different scales is problematic. Anchored in mini-DST-derived permeability, this study endeavors to integrate various sources of permeability, leading to reservoir description in a turbidite sandstone reservoir in the Sabah basin, Malaysia.

Ordinarily, pressure-transient-test data recorded during a mini-DST operation differ significantly from data gathered during a conventional DST. Even though test quality was excellent, interpretation challenges were numerous in this well. Consequently, multidisciplinary information was brought to bear for integration of data derived from mini-DSTs. Other sources of information included sidewall cores, spot pressure measurements, nuclear magnetic resonance (NMR), and microelectrical imaging logs. This case study demonstrates that, in this particular setting, the use of mini-DSTs was cost-effective and yielded the subsurface information required to plan field-development options.
A Comparison of Stochastic Data-Integration Algorithms for the Joint History Matching of Production and Time-Lapse-Seismic Data
Authors: Jin L.. , Alpak F.O.. O. , van den Hoek P.. , Pirmez C.. , Fehintola T.. , Tendo F.. , Olaniyan E..
Published: November 2012

Quantitative integration of spatial and temporal information provided by time-lapse (4D) -seismic surveys to dynamic reservoir models calls for efficient and effective data-integration algorithms. We carry out a comprehensive comparison of stochastic optimization methods using both a synthetic and a field case.

Our first case is a challenging synthetic test problem known as the Imperial College Fault Model (ICFM). The methods of very-fast simulated annealing (VFSA), particle-swarm optimization (PSO), and the neighborhood algorithm (NA) are compared in terms of convergence characteristics, data-match quality, and posterior model-parameter distributions. On the basis of the knowledge developed from the ICFM problem, we isolate VFSA and PSO and evaluate their performance further on a field case involving a deepwater reservoir undergoing waterflooding. The field case has a reasonably long production history and good-quality 3D- and 4D-seismic data, allowing the construction of a geologically consistent model by means of dynamic calibration. As such, it constitutes a relevant field test for joint seismic/production history matching. We assess the data-match characteristics and the quality of dynamic forecasts delivered by VFSA and PSO in the field case.

Practical guidelines are developed over the course of these studies for selecting a "fit-for-purpose" optimal method for joint history-matching workflows. Our results show that PSO, a population-based method, incurs relatively more computational expense at a given iteration but exhibits good convergence characteristics and provides multiple history-matched models. The PSO method has emerged as more effective compared with the NA and VFSA methods in the ICFM problem. It was also quite effective on the field application. On the other hand, the VFSA method requires comparatively more iterations to converge because of its sequential nature, but it has advantageous features when moderate computing resources are available.
Multiscale Gas Transport in Shales With Local Kerogen Heterogeneities
Authors: Yucel Akkutlu I.. , Fathi Ebrahim
Published: November 2012

On the basis of micro- and mesoscale investigations, a new mathematical formulation is introduced in detail to investigate multiscale gas-transport phenomena in organic-rich-shale core samples. The formulation includes dual-porosity continua, where shale permeability is associated with inorganic matrix with relatively large irregularly shaped pores and fractures, whereas molecular phenomena (diffusive transport and nonlinear sorption) are associated with the kerogen pores. Kerogen is considered a nanoporous organic material finely dispersed within the inorganic matrix. The formulation is used to model and history match gas-permeation measurements in the laboratory using shale core plugs under confining stress. The results indicate significance of molecular transport and strong transient effects caused by gas/solid interactions within the kerogen. In the second part of the paper, we present a novel multiscale perturbation approach to quantify the overall impact of local porosity fluctuations associated with a spatially nonuniform kerogen distribution on the adsorption and transport in shale gas reservoirs. Adopting weak-noise and mean-field approximation, the approach applies a stochastic upscaling technique to the mathematical formulation developed in the first part for the laboratory. It allows us to investigate local kerogen-heterogeneity effects in spectral (Fourier-Laplace) domain and to obtain an upscaled "macroscopic" model, which consists of the local heterogeneity effects in the real time—space domain. The new upscaled formulation is compared numerically with the previous homogeneous case using finite-difference approximations to initial/boundary value problems simulating the matrix gas release. We show that macrotransport and macrokinetics effects of kerogen heterogeneity are nontrivial and affect cumulative gas recovery. The work is important and timely for development of new-generation shale-gas reservoir-flow simulators, and it can be used in the laboratory for organic-rich gas-shale characterization.
Lattice Boltzmann Method for Simulation of Shale Gas Transport in Kerogen
Authors: Fathi Ebrahim , Akkutlu I. Yucel
Published: November 2012

Fluid mechanics of natural gas in organic-rich shale involves nanoscale phenomena that could lead to potential non-Darcy effects during gas production. In general, these are low-Reynolds-number and noncontinuum effects and, more importantly, pore-wall-dominated multiscale effects. In this study, we introduce a new lattice Boltzmann method (LBM) to investigate these effects numerically in simple pore geometries. The standard method was developed in the 1980s to overcome the weaknesses of lattice gas cellular automata and has emerged recently as a powerful tool to solve fluid dynamics problems, in particular in the areas of micro- and nanofluidics. The new approach takes into account molecular-level interactions by use of adsorptive/cohesive forces among the fluid particles and defining a Langmuir-slip boundary condition at the organic pore walls. The model allows us to partition mass transport by the walls into two components: slippage of free gas molecules and hopping (or surface transport) of the adsorbed gas molecules. By use of the standard 2D D2Q9 lattice, low-Reynolds-number gas dynamics is simulated in a 100-nm model organic capillary and later in a bundle of smaller-sized organic nanotubes. The results point to the existence of a critical Knudsen-number value for the onset of laminar gas flow under typical shale-gas-reservoir pressure conditions. Beyond this number, the predicted velocity profile shows that the mechanisms of slippage and surface transport could lead to molecular streaming by the pore walls, which enhances the gas transport in the organic nanopores. The work is important for development of new-generation shale-gas-reservoir flow simulators, and it can be used in the laboratory for organic-rich-shale characterization.
Early Symptom Detection on the Basis of Real-Time Evaluation of Downhole Conditions: Principles and Results From Several North Sea Drilling Operations
Authors: Cayeux Eric , Daireaux Benoît , Wolden Dvergsnes Erik , Sælevik Gunnstein
Published: November 2012

During drilling operations, downhole conditions may deteriorate and lead to unexpected situations that can result in significant delays. In most cases, warning signs of the deterioration can be observed in advance, and by taking proactive actions, drillers can avoid serious incidents such as packoffs or stuck pipes. A new analysis methodology, relying on an automatic real-time computer system, has been developed to detect those early indicator conditions.

The methodology involves constantly computing the various physical forces acting inside the well (mechanical, hydraulic, and thermodynamic). These physical forces are coupled by an automatic model calibration, which then gives a reliable picture of the expected well behavior. Through analysis of the deviations between modeled and measured values, an estimation of the current state of the well is derived in real time. Changes in the well condition are an early warning of deteriorating well conditions. This paper precisely describes the real-time analysis and the results during some drilling operations.

The software has been used for monitoring 15 unique wells located in five different North Sea fields. All major situations were signaled in advance at different event time scales: Rapidly changing downhole conditions (such as pulling a drillstring into a cuttings bed) were typically detected 30 minutes ahead of the actual event, medium-duration deteriorations were detected up to 6 hours before the incident, and slow-changing downhole conditions were signaled up to 1 day in advance. Several examples that illustrate the detected incidents over distinct time periods are described.

The availability of good-quality real-time data streams makes it possible to implement such analysis tools in an integrated operation setup. Early symptom detection can be used to make decisions in a timely fashion, on the basis of quantitative performance indicators rather than subjective feelings and personal experience.
Block Model for Growth of Steam-Heated Zone in Oil-Bearing Naturally Fractured Carbonate Reservoirs
Authors: Closmann Philip J.
Published: November 2012

A model for steam injection into naturally fractured carbonate reservoirs provides a method of calculating the volume of heated formation for a given amount of steam, provided that the assumptions of the model are satisfied. The model represents the fractured reservoir by a system of blocks, dependent on fracture spacing and dimensions. The amount of oil mobilized can be estimated from prior measurements of oil saturation and laboratory tests of oil-displacement efficiency. Results comparable to observations are obtained. In addition, the temperature distribution along the direction of propagation in the reservoir may also be estimated, providing a guide to variation in the local oil mobility. These results can assist in evaluating the effectiveness of steam injection in the recovery of oil from naturally fractured formations.
History Matching Time-Lapse Surface-Gravity and Well-Pressure Data With Ensemble Smoother for Estimating Gas Field Aquifer Support—A 3D Numerical Study
Authors: Glegola M.. , Ditmar P.. , Hanea R.G.. G. , Eiken O.. , Vossepoel F.C.. C. , Arts R.. , Klees R..
Published: November 2012

Water influx is an important factor influencing production of gas reservoirs with an active aquifer. However, aquifer properties such as size, porosity, and permeability are typically uncertain and make predictions of field performance challenging. The observed pressure decline is inherently nonunique with respect to water influx, and large uncertainties in the actual reservoir state are common. Time-lapse (4D) gravimetry, which is a direct measure of a subsurface mass redistribution, has the potential to provide valuable information in this context.

Recent improvements in instrumentation and data-acquisition and -processing procedures have made time-lapse gravimetry a mature monitoring technique, both for land and offshore applications. However, despite an increasing number of gas fields in which gravimetric monitoring has been applied, little has been published on the added value of gravity data in a broader context of modern reservoir management on the basis of the closed-loop concept. The way in which gravity data can contribute to improved reservoir characterization, production-forecast accuracy, and hydrocarbon-reserves estimation is still to be addressed in many respects.

In this paper, we investigate the added value of gravimetric observations for gas-field-production monitoring and aquifer-support estimation. We perform a numerical study with a realistic 3D gas field model that contains a large and complex aquifer system. The aquifer support and other reservoir parameters (i.e., porosity, permeability, reservoir top and bottom horizons) are estimated simultaneously using the ensemble smoother (ES). We consider three cases in which gravity only is assimilated, pressure only is assimilated, and gravity and pressure data are assimilated jointly. We show that a combined estimation of the aquifer support with the permeability field, porosity field, and reservoir structure is a very challenging and nonunique history-matching problem, in which gravity certainly has an added value. Pressure data alone may not discriminate between different reservoir scenarios. Combining pressure and gravity data may help to reduce the nonuniqueness problem and provide not only an improved gas- and water-production forecast and gas-in-place evaluation, but also a more-accurate reservoir-state description.
New Type Curves for Modeling Productivity of Horizontal Well With Negative Skin Factors
Authors: Nie R.-S.. -S. , Jia Y.-L.. -L. , Meng Y.-F.. -F. , Wang Y.-H.. -H. , Yuan J.-M.. -M. , Xu W.-F.. -F.
Published: November 2012

This paper first establishes a comprehensive semianalytical model for a horizontal well in a homogeneous, dual- or triple-porosity reservoir. By taking a negative-skin approach, including Laplace transform, separation of variables, and inverse Laplace transform, we obtain the solutions in a unified formula for both constant-rate production and constant-wellbore-pressure production. In the model, we consider a set of rich boundary conditions, including infinite reservoir and closed or constant-pressure boundary conditions for the top, bottom, and side of the bounded reservoir. Consequently, we plot a series of new standard log-log type curves and make a clear observation of different flow periods (e.g., early radial flow, hemiradial flow, linear flow, and late pseudoradial flow) from negative-skin type curves. We make a comparison between the solutions using the negative-skin approach and conventional solutions, which shows that there are some small differences between the two methods. We also analyze the type-curve characteristics for horizontal-well production in dual- and triple-porosity reservoirs, which shows that the derivative curves are V-shaped for dual media and W-shaped for triple media. Finally, we perform well-test interpretations for a horizontal well with positive skin and a horizontal well with negative skin and bottomwater, which shows that our new model performs well against the real field data.
Intelligent Prediction of Differential Pipe Sticking by Support Vector Machine Compared With Conventional Artificial Neural Networks: An Example of Iranian Offshore Oil Fields
Authors: Jahanbakhshi Reza , Keshavarzi Reza , Aliyari Shoorehdeli Mahdi , Emamzadeh Abolqasem
Published: November 2012

Differential pipe sticking (DPS) is one of the most conventional and serious problems in drilling operations that imposes some extra costs to companies. This phenomenon originates mainly from improper mud properties, bottomhole assembly (BHA) (contacting area), still pipe time, and differential pressure between the formation and the drilling mud. Investigation on various conditions that lead to DPS makes it possible to develop some preventive treatments to avoid this problem's occurrence. In the past, statistical methods were applied in this area, but recently artificial neural network (ANN) approaches are frequently being used. ANNs have some priorities over conventional statistical methods such as the model-free form of predictions, tolerance to data errors, data-driven nature, and fast computation. On the other hand, the designed ANNs have some shortcomings and restrictions as they are developed to predict problems. In this paper, to solve most of the existing disadvantages of ANNs, a novel support-vector machine (SVM) approach has been developed to predict a DPS occurrence in horizontal and sidetracked wells in Iranian offshore oil fields. The results from the analysis have shown the potential of the SVM and ANNs to predict DPS, with the SVM results being more promising.
Ionomic Characterization of Maize Kernels in the Intermated B73 × Mo17 Population
Authors: Baxter Ivan R. , Gustin Jeffery L. , Settles A. Mark , Hoekenga Owen A.
Published: November 2012

Dietary mineral deficiencies affect nearly half of the people on our planet, largely due to poverty. Enhancing nutritional quality—or biofortification—represents an efficient and sustainable potential solution to this massive public health problem. To create biofortified crops, one must understand the genetic and environmental factors that influence the ionome, or collection of mineral nutrients, in the target organism and tissue. We describe the use of quantitative trait loci (QTL) mapping to characterize the maize (Zea mays L.) grain ionome illustrated by the intermated B73 × Mo17 (IBM) recombinant inbred population. Ionomic profiling was applied to field grown materials from Florida, North Carolina, and New York. Twenty‐seven QTL were detected for 10 traits derived from the North Carolina and New York grown maize explaining between 4 and 46% of the variance observed. For biofortification to succeed, QTL effective in multiple environments need to be the targets for improvement efforts. Florida grown maize were sampled shallowly to provide a low cost dataset to evaluate the models based on the combined North Carolina and New York traits. Twenty‐five QTL were detected as significant in two or more locations using ANOVA on the original single location and/or site data; 12 QTL were found to be significant in Florida. While this strategy may have not detected every potential QTL from our data, we suggest these QTL effective in multiple environments represent a starting position for the biofortification of maize grain.
Long‐term Genetic Improvement and Genetic Diversity of Croatian Flue‐cured Tobacco (Nicotiana tabacum L.) Cultivars
Authors: Šarčević H. , Gunjaća J. , Budimir A. , Boić M. , Bolarić S. , Bukan M. , Lewis R. S. , Kozumplik V.
Published: November 2012

Use of breeding methodologies to develop improved flue‐cured tobacco (Nicotiana tabacum L.) cultivars in Croatia has been performed since the early 1960s. Since that time, >20 cultivars have been released. Between 1973 and 2007, only nine of these cultivars have been accepted by tobacco growers and the tobacco industry, however. To quantify the genetic improvement of agronomic traits and associated changes in morphological and chemical characters during this period of time, these nine cultivars were grown and studied in experiments conducted at three Croatian locations for 3 yr. Trait stability and genetic diversity of the same cultivars were also investigated. Regression analysis of agronomic traits over year of cultivar release showed a significant annual increase in yield of 17.39 kg ha−1 yr−1, price of $0.009 kg−1 yr−1, and value of $56.50 ha−1 yr−1. These increases can be attributed to genetic improvement of new cultivars. During the 1973–2007 time period, the average number of leaves increased significantly. Over the same period, nicotine content decreased slightly and reducing sugar content increased significantly. Newer cultivars were also found to have higher yield stability as compared to older cultivars. Genetic diversity among the studied cultivars as revealed by amplified fragment length polymorphism genetic markers was relatively low. Unweighted pair group method using arithmetic averages analysis clustered the cultivars in accordance with their pedigrees.
Potential of Some Hybrid Maize Lines to Induce Germination of Sunflower Broomrape
Authors: Ma Yongqing , Jia Jinnan , An Yu , Wang Zhong , Mao Jianchang
Published: November 2012

Orobanche cumana Wallr. (sunflower broomrape) is a devastating root parasitic weed, causing enormous crop losses throughout the world. Maize (Zea mays L.) is able to induce germination of at least two Orobanche species. Our question was whether or not maize has potential to be used as a “trap crop” for O. cumana. To answer this question, we screened four maize hybrids and their parental lines for their ability to induce O. cumana germination. The results indicated that rhizosphere soil, rhizosphere soil extracts, root extracts, and shoot extracts from three of the four maize hybrids and their parental lines induced significant O. cumana germination. Root extracts generally induced higher germination rates than shoot extracts. Ten‐fold dilutions of the extracts generally induced higher germination rates than either undiluted extracts or 100‐fold dilutions. The ability to induce germination varied significantly among maize hybrid and inbred lines, with the hybrid 3255 × 335 and its parental lines generally inducing the highest O. cumana germination rates. The genetic mechanism for the production of the chemical stimulant that induces O. cumana germination needs to be analyzed further; however, we propose that there is potential for a breeding program to be developed to produce maize lines with greater ability to induce O. cumana germination. These lines could be used as trap crops for the control of this devastating root parasitic weed.
Molecular Mapping of the Mutant fap4(A24) Allele for Elevated Palmitate Concentration in Soybean
Authors: Oltmans‐Deardorff Sheilah E. , Fehr Walter R. , Welke Grace A. , Shoemaker Randy C. , Graham Michelle A.
Published: November 2012

Soybean [Glycine max (L.) Merr.] oil with an elevated palmitate concentration is useful for some food and industrial applications. The objective of this study was to map the genetic location of the fap4(A24) allele that controls an increase in palmitate concentration and to identify molecular markers that can be used for marker‐assisted selection (MAS) of the allele. A cross was made between the mutant line A24(fap4fap4) and the cultivar Archer(Fap4Fap4), and DNA was collected from 22 F4 plants with normal palmitate and 22 F4 plants with elevated palmitate concentration. The DNA samples were analyzed on the soybean single nucleotide polymorphism (SNP) chip developed by Monsanto Co. Publicly available simple sequence repeat (SSR) markers were used to fine‐map the allele. On the basis of these molecular analyses, the fap4(A24) allele was mapped to chromosome 3 (linkage group N) in an area between SSRs BARCSOYSSR_03_1260 and BARCSOYSSR_03_1313. Seven SSRs and a SNP were identified in the region that perfectly differentiated the plants which were homozygous for the fap4(A24) allele for elevated palmitate or the Fap4 allele for normal palmitate. The public SNP and SSRs should be useful for MAS of the fap4(A24) allele in segregating populations.
Forage Rye Improvement in the Southern United States: A Review
Authors: Newell Mark A. , Butler Twain J.
Published: November 2012

Rye (Secale cereale L.) is an important crop worldwide for grain and forage production. Stocker cattle (Bos spp.) production in the southern United States relies on rye for forage from autumn to spring when warm‐season perennials remain dormant. Because rye has high‐stress tolerance with respect to both soil and environment, it fills a particular niche that spans the winter months for the region. Rye forage yield has not improved over time, due in part to limited breeding effort. Many of the cultivars currently grown in the region were released as early as the 1950s. Similar to other forage crops, gains in forage yield have been small or nonexistent; therefore, an evaluation of the crop in relation to past and current breeding strategies could contribute to the future improvement of the crop. The objectives of this manuscript are to review the rye crop in relation to its cropping system, the genetic considerations for rye in relation to breeding, and past and current breeding efforts and selection processes and then to propose breeding methodologies for the improvement of rye with major focus on forage yield. Methods of selection that rely on family performance in multienvironment trials are recommended. With advancements in breeding methods, rye poses a unique opportunity among the forage crops to enable rapid cycling for development of improved cultivars.
Genetically Characterizing a New Indica Cytoplasmic Male Sterility with Oryza glaberrima Cytoplasm for Its Potential Use in Hybrid Rice Production
Authors: Huang Feng , Fu Xi , Efisue Andrew , Zhang Sisong , Xie Guosheng , He Wenchuang , Nevame Adedze Y. M. , Jin Deming
Published: November 2012

Cytoplasmic diversification is of vital importance to avoid the genetic vulnerability of hybrid rice (Oryza sativa L.). A new indica cytoplasmic male sterility (CMS), designated African rice (AF) CMS, has been derived from interspecific crosses using African rice (Oryza glaberrima Steud.) as the cytoplasmic donor and genetically characterized for its potential use. The AF CMS lines were completely sterile whereas the fertility of its F1 hybrids was readily restored. The restoration–maintenance relationship of AF CMS was consistent with that of sporophytic wild abortive (WA) and Indonesian paddy (ID) CMS but different from the gametophytic Honglian (HL) CMS. Specific banding patterns for AF CMS were identified by amplified fragment length polymorphism (AFLP). The AFLP markers can be used to detect genetic purity of seed stocks of AF CMS lines and their hybrids. Fertility segregation in F2 populations of crosses between AF CMS lines and an introgression restorer line corresponded to a 3:1 fertile:sterile ratio, indicating a single major dominant restorer gene was involved. The fertility‐restoring gene was located on chromosome 10 between simple sequence repeat (SSR) markers RM304 and RM6100 at a genetic distance of 1.25 cM from RM6100. Molecular assays confirmed the introgression of a major restorer gene from O. glaberrima into the O. sativa genome. We conclude the new AF CMS system should be of great potential use in hybrid rice production.
Mineralization of Carbon‐14‐Labeled Plant Residues in Conventional Tillage and No‐Till Systems
Authors: Sharifi Mehdi , Zebarth Bernie J. , Burton David L. , Drury Craig F. , Grant Cynthia A.
Published: November 2012

Tillage systems are known to influence the quantity and quality of soil organic C (SOC); however, it is unclear if tillage also changes the soil catabolic capacity (the ability to decompose C substrates). This study compared soils from two contrasting tillage systems, no‐till (NT) vs. conventional tillage (CT), with respect to their ability to catabolize a common 14C‐labeled substrate. Intact core samples from the 0‐ to 5‐cm soil depth under CT and the 0‐ to 5‐ and 10‐ to 15‐cm depths under NT were collected after 14 yr of winter wheat (Triticum aestivum L.)–corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation. Soil cores received a common substrate (14C‐labeled wheat residues) either surface applied or incorporated into the soil. Decomposition of the 14C‐labeled residues, soil mineral N concentration, and soil microbial biomass 14C (MB14C) were monitored for 86 d at 25°C. Respiration of 12CO2 from native SOC was greater at 0 to 5 cm under NT than CT but did not vary with depth under NT; there was no significant effect of tillage system or depth under NT or residue placement on respiration of residue 14CO2. Incorporation of 14C residues increased MB14C compared with surface application, indicating a greater efficiency of C utilization. For the soils and residues used in this experiment, there was no evidence of an effect of tillage system on soil catabolic capacity, and differences in soil microbial activity between tillage systems were attributed only to differences in the quantity and quality of C substrates.