bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation and Removal of Tidal Effects From Pressure Data
Authors: Zhao Y. , Reynolds A. C. 
Published: December 2007

Abstract
We consider field pressure data from two wells, one offshore and one onshore. The onshore well is shut-in and experiences only a very small pressure decline due to inter-ference whereas, in the offshore case, the late time buildup data appears to be severely corrupted by ocean tidal effects. The objectives in both cases are to determine the tidal signal which can be used to estimate formation compressibility and to remove the tidal signal from the measured data.
For the onshore well, we use a Savitsky-Golay filter to smooth the pressure data. Subtracting the smooth data from the measured signal yields a modified signal which ideally represents the earth tidal signal plus measurement error. As the main harmonic components of the earth tidal signal are known, we perform a least-squares fit of the modified pressure data with a series of sines and cosines which contain only the known frequencies of the earth tide. By subtracting the series obtained by least squares fitting from the true signal, we remove the effect of the earth tide.
In the offshore case, the time span of the data that is severely affected by tidal effects is too short to use the Savitsky-Golay filter with confidence. As the reservoir pressure change due to the tides is well-approximated by a damped and delayed version of the sea floor response, a least squares fit of the data with a function which follows the underlying buildup trend plus an attenuated-delayed response of the measured seafloor pressure trace allows one to obtain a good estimate of the attenuation factor and time delay so that the tidal component of the bottom-hole pressure change can be determined and removed from the measured pressure.
Optimizing the Productivity of Gas/Condensate Wells
Authors: Shi C. , Horne R. N. , Li K. 
Published: December 2007

Abstract
Gas-condensate reservoirs exhibit complex phase and flow behaviors due to the appearance of condensate banking in the near-well region. A good understanding of how the condensate accumulation influences the productivity and the composition configuration in the liquid phase is very important to optimize the producing strategy, to reduce the impact of condensate banking, and to improve the ultimate gas recovery.
This study addressed several issues related to the behavior of the composition variation, condensate saturation build-up and condensate recovery during the gas-condensate producing process. A key factor that controls the gas-condensate well deliverability is the relative permeability, which is influenced directly by the condensate accumulation. The accumulated condensate bank not only reduces both the gas and liquid relative permeability, but also changes the phase composition of the reservoir fluid, hence reshapes the phase diagram of reservoir fluid and varies the fluid properties. Different producing strategies may impact the composition configuration for both flowing and static phases and the amount of the liquid trapped in the reservoir, which in turn may influence the well productivity and hence the ultimate gas and liquid recovery from the reservoir. Changing the manner in which the well is brought into flowing condition can affect the liquid dropout composition and can therefore change the degree of productivity loss.
In this study, compositional simulations of multicomponent gas-condensate fluids were conducted at field scale to investigate the composition and condensate saturation variations. Different producing strategies have been compared, and the optimum producing sequences are suggested for maximum gas recovery. A core flooding experiment with two- component synthetic gas-condensate was designed and constructed to model gas-condensate production behavior from pressure above the dew-point to below. Experimental observations of gas-condensate production confirm the dramatic changes in the liquid composition seen in the simulations.
Sustained Competitive Advantage Through Structured Mentoring
Authors: Arango G. , Han P. , Rousseau M. 
Published: December 2007

Abstract
"Knowledge is like money. To be of value, it must circulate, and in circulation it can increase in quantity and, hopefully in value." (Louis L'Amour).
Sustained success and steady growth require organizations to develop and retain a core of culture, relationships and critical knowledge and skills. Capitalizing on the strengths of several disciplines such as competency-based training, knowledge management, and structured mentoring programs, organizations can reach these goals and offer their employees opportunities for professional development and career advancement that would not otherwise be possible. In this paper, we discuss an approach to structured mentoring aimed at the effective and reliable transfer of corporate culture, relationships, and knowledge. We identify key practices and tools and share lessons learned from experience.
3D Numerical Simulator for Horizontal-Well Gravel Pack
Authors: Ojo K. P. , Osisanya S. O. , Ayeni K. B. 
Published: December 2007

Abstract
A 3-D numerical simulator for horizontal well gravel packing is developed. The model was developed based on the fundamental laws of physics by solving for an overall conservation of forces during the placement of the gravel in the horizontal well bore. The equations of continuity, motion, and deposition are simultaneously solved to give a 3-D solution of the gravel pack process. The modeling equations consist of five partial differential equations (PDEs) with five dependent variables, all of which were solved simultaneously. The system of PDEs was approximated using the central-difference finite-difference approximations method. The settling effect of slurry using the type of fluid, proppant and flow conditions existing in gravel pack operations in horizontal wells were also included in the model.
The model is used for simulating the gravel pack process and determining the effectiveness and pack efficiency of the gravel pack job. This 3-D simulator can be used to simulate special situations in which significant leakage into the formation occurs during gravel packing. The simulator is particularly suitable for deep horizontal wells because the hindered settling effect prevalent in the long vertical section of deep horizontal wells is accounted for in the modeling equations. The simulator was illustrated by simulating some horizontal gravel-pack jobs reported in the literature.
Tracing Streamlines on Unstructured Grids from Finite Volume Discretizations
Authors: Matringe S. F. , Juanes R. , Tchelepi H. A. 
Published: December 2007

Abstract
The accuracy of streamline reservoir simulations depends strongly on the quality of the velocity field and the accuracy of the streamline tracing method. For problems described on complex grids (e.g., corner-point geometry or fully unstructured grids) with full-tensor permeabilities, advanced discretization methods, such as the family of multipoint flux approximation (MPFA) schemes, are necessary to obtain an accurate representation of the fluxes across control volume faces. These fluxes are then interpolated to define the velocity field within each control volume and streamlines are integrated. Existing methods for the interpolation of the velocity field and integration of the streamlines do not preserve the accuracy of the fluxes computed by MPFA discretizations.
Here we propose a new method for the reconstruction of the velocity field with high-order accuracy from the fluxes provided by MPFA discretization schemes. This reconstruction relies on a correspondence between the MPFA fluxes and the degrees of freedom of a mixed finite-element method (MFEM) based on the first-order Brezzi-Douglas-Marini space. This link between the finite-volume and finite-element methods allows the use of flux reconstruction and streamline tracing techniques developed previously by the authors for mixed finite elements. After a detailed description of our streamline tracing method, we study its accuracy and efficiency using challenging test cases.
Subsea Multiphase Pressure Boosting and a New Approach for Speed Control Using a Hydrodynamic Variable-Speed Drive
Authors: Scott S. L. , Xu J. , Lenz C. 
Published: December 2007

Abstract
Interest in the subsea deployment of multiphase pumps and wet-gas compressors has grown as companies search for methods to improve recoveries and economics for subsea wells. Subsea pressure boosting technologies are also seen as vital in providing access to deepwater oil and stranded gas reservoirs. While multiphase pumping has been proven onshore, operators have been hesitant to deploy this technology subsea due to the high costs and inherent risks associated with the first application of a new technology. This paper examines various types of subsea multiphase pumps and wet-gas compressors and discusses the special issues associated with subsea operation. Multiphase pressure boosting requires a wide torque and speed range due to significant load changes, triggered by changes in the gas volume fraction (GVF). This paper introduces and describes a hydrodynamic variable speed drive that can be utilized with both multiphase pumps and wet-gas compressors. This variable speed drive is arranged between a fixed speed motor and the multiphase boosting device and appears to offer several distinct advantages for subsea operation. The Voith Turbo EL6 torque converter was installed and tested with a twin-screw pump under multiphase condition. Results of testing under slug flow conditions are presented along with observations regarding the use of a torque converter for speed control.
Effect of Layered Heterogeneity on Fracture Initiation in Tight Gas Shales
Authors: Suárez-Rivera R. , Green S. J. , McLennan J. , Bai M. 
Published: December 2007

Abstract
Hydraulic fracturing is the requisite methodology for completing nano-darcy matrix permeability tight gas shales. Commercial success in producing these reservoirs depends to a large extent on successful hydraulic fracturing. There is growing evidence that initiating hydraulic fractures from horizontal wellbores is often difficult, and requires abnormally high treating pressures. In this paper, we show that the combination of high stiffness, significant elastic anisotropy, and coupled elastic property and horizontal stress development, in tight gas shale reservoirs results in complex near-wellbore stress concentrations, not observed in isotropic rocks. Using finite element analysis (FEA) and numerical modeling, with continous mechanics and transverse anisotropic elasticity, we provide insights on the stress concentration resulting from various conditions of stress (normal and reverse faulting) and material properties. We also provide a simplified methodology for first-pass calculation of these stress concentrations, and thus for predicting the potential for problems during fracture initiation. Modeling near-wellbore effects in horizontal completions in anisotropic shales is straightforward. However, the calculations require a larger set of material properties (4 elastic constants), as well as in-situ stresses, and reservoir pressure.
Production Improvement Water Shutoff for White Tiger Field
Authors: Chan Keng Seng , Lam Duong Danh , Ivanov Aleksey , Apisitsareekul Kiam P. , Hai Le Viet , Nghi Nguyen Chinh , Hung Vuong Quoc , Lang Le Dinh 
Published: December 2007

Abstract
Oil production from some of wells in the White Tiger field producing from a fissured Basement reservoir; have been impaired by excessive water production. Excess water not only reduced the artificial lift efficiency, but also imposed various damages to the oil zones.
Since 2002, a joint industrial project was set up to study the feasibility of performing water shutoff treatments in the open-hole completion oil wells. The study involved evaluation of a high temperature polymer base water shut-off fluid for deep penetration of the fissure formation and a micro-fine cement system for sealing off the water entries. Based on this study, a cost-effective chemical treatment method was progressively developed. In 2005, the treatments were performed through-tubing with and without isolation packers.
Two Candidate wells were having 6.5″ open-hole size, at approximately 4,200 meter TD, and 150 deg C reservoir temperature. The water cut were 95% in one well and 30% in the other well. It was found that these two wells certainly had big difference in fluid injectivity, and original designed treatment was modified on site. This paper summarizes key lessons learnt including tool and packer conveyance, mixing and pumping of water shut-off fluids under offshore rig and wellsite conditions. It also shares a method of post treatment production evaluation and suggests operational change to improve the production.
Modern Approach to Estimation of Uncertainty of Predictions With Dynamic Reservoir Simulation—A Case Study of a German Rotliegend Gas Field
Authors: Junker H. J. , Plas L. , Dose T. , Little A. J. 
Published: December 2007

Abstract
A deep German onshore Rotliegendes gasfield in a complex sedimentary and structural environment is subject to evaluation of the remaining potential for additional wells and possible recovery acceleration.
A graben structure filled with aeolian sediments in an overall depth of about 4900m comprises the dry gas bearing reservoir. The field is developed by a limited number of expensive wells with a relatively wide well spacing. The wells face complicated drilling conditions and a necessary deviation to honour environmental issues which severely limit the number of well site locations.
The quality of the 3D seismic is limited because of Zechstein salt intrusions in the overburden. Hence the structural and interpreted fault models are subject to significant uncertainties. Characterisation of aeolian sedimentary facies distribution and quality, which suffers from diagenetic effects, is achieved by a geostatistical approach. The model is mainly based on information from cores and logs. Seismic information could only be used to guide the distribution of the aeolian reservoir facies and a probably unproductive fanglomerate facies type.
One main question is the level of compartmentalisation of the field due to faults and flow barriers related to reservoir facies distribution. During the dynamic modelling process possible scenarios are checked against the observed production data regarding communication and GIIP distribution. This gives a range of possibilities leading to a significant uncertainty regarding the prediction of future production and the effect of acceleration wells. There is room for only a few more wells. The decision where to place these is supported by the integrated modelling approach. This has been chosen to address a wide range of uncertainty of both static and dynamic effects. The static effects have been addressed by a combination of geostatistical static reservoir modelling with fully 3D static uncertainty estimation.
The basis for the dynamic modelling part is a family of realisations defined by a process to identify "most diverse" representative scenarios out of bigger number of geological realisations. Computer aided history matching, experimental design and proxy solutions gave a very effective approach to handle the uncertainty estimation with the dynamic reservoir simulation. The fully integrated workflow allowed an optimized process to estimate the uncertainty of prediction within a limited time frame. The main subject of this paper is the process of dynamic reservoir simulation using these techniques and discussion of the results.
Fracture Acidizing: What Role Does Formation Softening Play in Production Response?
Authors: Nasr-El-Din H. A. , Al-Driweesh S. M. , Metcalf A. S. , Chesson J. 
Published: December 2007

Abstract
Fracture acidizing of carbonates has yielded increases in production in many areas of the world, but depending upon rock strength and reservoir closure pressure this response may be lower than expected. Also, as a result of rock strength and closure pressure, production may decline at a higher rate than after a proppant fracture treatment.
Laboratory results are presented describing the effect on strength reduction of limestone and dolomite formation samples after exposure to various acid systems. Formation samples were dry, saturated with potassium chloride water or saturated with synthetic oil prior to testing. Samples were exposed to neat, emulsified, gelled and crosslinked 15 wt% hydrochloric acids and each exhibited a differing effect on rock strength reduction. In addition, production responses are presented and compared with regard to type of acid system used for stimulation.
Underbalanced Operation Can Extend Its Antennae To Breach the Barriers of Conventional Method
Authors: Liu Gang , Qin Wengui 
Published: December 2007

Abstract
Under-balanced drilling has been using in China for several years. UBD technology can reduce mud weight in the maximum way, and is a valuable method of minimizing formation invasion related problems. Some oilfields have found its strongpoints in exploration and development. This paper demonstrates that UB sometimes can be used to break through the barriers of HPHT, to prevent the H2S from branching out, to solve the problem of narrow margin between the formation fracture pressure and pore pressure, to find a new producing pay, and to drill through the lost circulation zone etc. So it could be a way of using UB tools or UB technology to solve the engineering difficult problem and to keep the well in safe, at the same time UB has shortage itself and will bring some troubles if it not be properly designed or controlled. Several problems in using UB tools and technology will be discussed, especially on the methods of pressure control. To enhance the reliability of UB practice, a new design choke control panel has been used in well site. This equipment has the multifunction of drilling engineering data acquisition, data transimission and storege, and especially has the function of pressure automatic control. The result of laboratory test illuminates that the function of software and data acquisition of the system work well. The result of 3 well site tests and 2560 hours work illuminates that the functions of hardware, software and the pressure auto-control of the equipment work well. It is valuable for improving UBD operation and safety. UB tools give us the approach of reducing mud density and offer the well safety in a certain extent, so we can use it in UB and NBD (near balance drilling), just for when and how much the new productivity and enhancement production has been gotten, not for when and how much the pressure difference has been remained.
Multicomponent OBC (4C) Imaging Over Pamberi, LRL Block, Offshore Trinidad
Authors: Johns T. D. , Vito C. , Clark R. , Sarmiento R. 
Published: December 2007

Abstract
Results from the P-P and P-Sv prestack time migration of a 2.5D four-component (4C) OBC seismic swath test acquired in 2004 over the Pamberi area in Block Lower Reverse L offshore Trinidad, are presented. The 4C swath acquisition consisted of twelve 100-m spaced source lines, shot into two parallel 15-km OBC receiver lines, separated by 400 m. A description of the processing applied to the recorded multicomponent (4C) seismic data, through curved-ray anisotropic Kirchhoff prestack time migration for both the compressional P-wave and mode-converted PSv-wave, is provided. Mode-converted shear-wave data acquired from 4C surveys allow for imaging where conventional seismic data are perturbed due to the presence of shallow gas and/or fluid in the pore spaces of the rock. Furthermore, mode-converted shear waves propagate with a different raypath than that of the compressional wave, thereby providing an alternative illumination of the subsurface target. As both the compressional P-wave and mode-converted S-wave record independent measurements of the same subsurface, more reliable rock properties can be uniquely determined, allowing for improved reservoir characterization and lithology prediction.
A conventional streamer 3D survey was acquired over the Pamberi area in 2003, but failed to image or resolve adequately the target reflectors comprising the reservoir under the main growth fault. Therefore, the purpose of the 4C swath test was to evaluate the potential of long-offset multicomponent technology for resolving stratigraphic interpretation in complex areas with challenging geology.
The processed images from both the compressional wave and mode converted shear waves are shown to illustrate the improvement in resolution at the reservoir prospect level which were not clearly evident on the previous conventional towed streamer 3D data volume.
Laboratory Hydraulic Fracturing Test on a Rock With Artificial Discontinuities
Authors: Casas L. , Miskimins J. L. , Black A. , Green S. 
Published: December 2007

Abstract
The design and subsequent results of a hydraulic fracturing test performed on a large block of high modulus and low permeability rock (Colton sandstone) are presented. The focus of this experimental study was to assess the effects of discontinuities on hydraulic fracture growth. A high viscosity fluid was used in order to provide fracture growth similar to actual field conditions. Fracture growth and its internal fluid pressure were monitored by fixed probes placed normal to the expected plane of propagation. Fracture tip arrivals were captured by the fixed pressure probes and showed a distinct fluid lag region (i.e., a lower fluid pressure region close to the fracture tip). The controlled laboratory experiments showed planar fracture propagation trends as expected from three-dimensional modeling.
The Evolution of Advanced Well Completions Results in Enhanced Well Productivity and Recovery in Saudi Aramco's Offshore Fields
Authors: Al Qudaihy D. S. , Al Qahtani H. B. , Sunbul A. H. , Hembling D. , Salerno G. 
Published: December 2007

Abstract
The Offshore sandstone reservoirs in Saudi Arabia are characterized by high production potential due to the nature of the reservoir, consisting of clean coarse sand with active bottom water aquifer and in some areas, a gas cap as drive mechanisms.
In recent years, horizontal wells have replaced conventional wells due to their improved deliverability and recovery efficiency. The initial completion method selected by Saudi Aramco for the horizontal wells was mainly cased hole cemented with selective perforation strategy. This completion method was troubled by non-uniform flow profiles, which drastically shortened the well production life reducing the benefit associated with the planned horizontal wells.
This paper will describe the concept of an innovative openhole completion strategy that has increased well productivity and recovery compared to past horizontal completion methods. The paper will show the evolution starting with the use of openhole completions completed with passive Inflow Control Devices (ICD) allowing production optimization by delivering uniform inflow along the entire horizontal section. The paper continues to discuss the benefits associated with the integration of the passive inflow control system with artificial lift (In situ gas lift and Electrical Submersible Pump (ESP) and finally reveals plans to couple passive inflow control with active intelligent well completion technology for multilateral wells. Actual field data will be presented to validate findings and support conclusions.