bluuebunny/crossref_metadata_2025_split huggingface dataset:
Remarkable Results from Water Shutoff Treatments Using a New Deep Penetrating Polymer System—Case Histories from South Umm Gudair Field, DZ-Kuwait/Saudi Arabia
Authors: Al-Mutairi Talal Z. , Shahid Mohammad A. , Reinhold Mark R. , Gazi Naz H. 
Published: December 2007

Abstract
The South Umm Gudair (SUG) field is located in the northwest corner of the Divided Zone (DZ) bordering Kuwait and Saudi Arabia. It represents the southern plunge of Umm Gudair field in Kuwait in the north. The field is producing from the Lower Cretaceous Ratawi Oolite reservoir that is capped by shale limestone sequences of the Ratawi Limestone. The field was discovered in 1966.
There has been significant increase in the water cut throughout the field. The production data in the recent past has shown an increase in water production in a number of wells (50% to 80% water cut) and a resulting drop in oil production.
The field was subjected to three different development phases. In each phase, the Oil Water Contact (OWC) was getting shallower with time. Production logs were run in several wells that indicated water encroachment in individual wells. The reservoir pressure has dropped considerably and all producing wells are completed with electrical submersible pumps.
Efforts made to control the high water cut by conventional mechanical plug back techniques of shutting off the lower perforations were successful in the past but it did not sustain for a longer period of time. The water cone would soon get bigger and encroach the higher perforations with increased water cut, thus the wells would be producing below their optimum potential. It was observed that some advanced technology which could delay the water encroachment more effectively was needed.
This paper describes the case histories of successful applications of a deep penetrating polymer system that was used to create an impermeable gel barrier in the reservoir around the well bore that could sustain long-term water shutoff results in these SUG wells. In addition, the understanding of the reservoir, geology, fluid flow mechanism, and systematic approach of treatment design with proper placement techniques, provided insight into these treatments' success and of limiting the uncertainties involved.
The system was applied to several SUG wells and in all these cases excellent water shutoff results were obtained. Specifically in the first well the water cut was reduced from 71% to less than 1% (0.9%). In another well the water cut was reduced from 72% to 3.4%. In all these cases the oil production was significantly increased.
In addition to the incremental oil gain there is a big reduction in the cost of lifting and handling of unwanted water production resulting in achieving great economic benefits.
The post-job analysis allowed further optimization of these processes, which are facilitating similar applications in the future.
A Novel Laboratory Method for Assessing the Erosional Characteristics of Mudcakes
Authors: Amanullah Md. 
Published: December 2007

Abstract
Design and development of superior drilling and drill-in fluids and also assessment of the effectiveness of mudcake cleaning from the borehole wall by cleaning systems require a good understanding of the fundamental phenomena associated with the erosional behaviour of mudcakes formed by different mud systems. Because of serious consequences of mudcake erosion on formation damage potential of drilling muds and mudcake cleaning prior to a cementation job, it is important to have a suitable, simple and field applicable method for predicting the erosional potential of mudcakes formed by muds of different chemical composition. The prediction of erosion behaviour is essential to screen and select appropriate mud additives and also to design new mud products for producing good quality mudcakes on the borehole wall. The technique and technology could provide a suitable means to assess the effectiveness of mudcake cleaning systems and help design such cleaning systems for removal of mudcake from the borehole wall.
Cakes formed by several water-based muds were evaluated using the newly developed technique. The testing has been performed with the simulation of hydrodynamic conditions corresponding to the drill collar-borehole annular section of a wellbore. The results indicate that the presence of electrolyte significantly increases the erosion coefficient of bentonite mudcake. Ionic fluid loss additives such as PAC (polyanionic cellulose) and CMC (carboxymethyl cellulose) reduced the erosion behaviour of salt water-based bentonite mudcake significantly. However, the presence of polyanionic fluid loss additive PAC caused a drastic reduction in the erosion characteristic of NaCl-based salt water mud compared to the presence of anionic fluid loss additive CMC. The presence of non-ionic fluid loss additive, modified starch shows little improvement of erosional behaviour of salt water-based mudcake. It seems to be that the electro-chemical forces of interactions of ionic fluid loss additives play a vital role in making a mudcake non-erodible. The variation of the erosional characteristic of the mudcakes is attributable to the physical, chemical and electrical properties of the cake forming mud additives and also the nature of the fabrics formed by these additives within the mudcake matrix.
Empirical Heat Transfer Model for Slug Flow and Bubble Flow in Vertical Subsea Pipes
Authors: Gao Changhong 
Published: December 2007

Abstract
The prediction of flow assurance related problems for subsea pipelines, such as paraffin deposition, alphaltene deposition, corrosion, hydrate formation, cold oil line startup etc, all partially rely on valid heat transfer models. Compared with single-phase heat transfer and two-phase hydraulics, two-phase heat transfer is much more complicated because the mechanisms of heat transfer for specific flow patterns are different.
A variety of empirical models have been developed for specific flow pattern of two-phase liquid-gas heat transfer. Some of them have been proved fairly accurate through research and literature review, such as Aggour model for bubble flow and Rezkallah model for slug flow both in vertical pipes. However, when these models are applied to subsea cooling conditions, the accuracy is not satisfactory.
In this paper, the basic knowledge of two-phase flow is introduced. A new empirical heat transfer model is developed for both slug flow and bubble flow in vertical subsea pipelines. Experimental data proves this model works better than the existing models. Literature review indicates that this is the first model that can be applied to two flow patterns. From the results seen, the model can predict good accuracy. The paper therefore recommends the application of this model.
Effective Approach to Horizontal Wellbore Clean-out of Calcium Carbonate Mud Cake in Sandstone Reservoirs
Authors: Uchendu Chike , Nwoke Linus , Arukhe James 
Published: December 2007

Abstract
This paper presents an effective and efficient approach for horizontal well bore cleanout of calcium carbonate mud cake.
The method utilizes a gelled organic acid system, which possesses the unique quality of retaining sufficient viscosity and stability during placement process but still remains active enough to dissolve the calcium carbonate mud cake while in the drain hole 1 . The system offers good leak off control, flow resistance, effective zone coverage and enough capability to flow back the dissolved mud cake to surface.
Ten wells in the Niger Delta were successfully treated with the new cleanout fluid and some of these wells are currently on well potential tests. The placement of the acid was "annulus in, wash pipe out", through the packer port, with the flapper valve on the packer isolating the acid in the drain hole from the brine above it immediately the wash pipe is pulled above the flapper valve. As treatment was incorporated into the initial completions activity, there was no additional CTU mobilization costs.
Field and laboratory results show that complete dissolution of calcium carbonate cake can take six hours and when in solution, can be retained for extensive time with stable viscosity and minimal leak off into the formation.
This paper will report results of laboratory tests carried out to achieve the operator requirements for the treatment fluid; highlight improvements on the initial fluid used and show the unique application and suitability of the gelled organic acid system for certain wells.
A Quick Look Kriging Technique for Reservoir Characterisation
Authors: Brown P. C. , Falade G. K. 
Published: December 2007

Abstract
Correct descriptions of reservoir rock heterogeneity provide useful input for simulation models and are essential for efficient reservoir management.
This paper discusses a novel kriging technique that uses sparse irregularly spaced permeability data to generate permeability values at other points within chosen grid blocks. A uniquely designed computer program, expressed in FORTRAN provides solution to the sequence of algorithms required for the solution of the kriging system in the absence of more sophisticated kriging models. Results obtained from the model allows for relatively cheap and reasonably accurate characterization of heterogeneous reservoirs.
Consolidating the Gains of Rotary Steerable Drilling in the Niger Delta
Authors: Inyang Etido , Edghill Peter , Aniche Victor , Choo Dominick , Adewumi Femi , Olaye Friday , Ogunnoiki Judah 
Published: December 2007

Abstract
A rapid acceptance of the rotary steerable drilling system by the drilling teams of the Niger Delta operators has been occasioned by the increasing difficulties associated with directional drilling in this region. Excluding new discoveries in the deep offshore region, operators have focussed largely on finding economic and competitive ways of exploiting the mature fields already developed beyond the reach of available technologies, and the rotary steerable system presents the opportunity for further development of these fields.
A major operator deployed the rotary steerable system for the first time in Nigeria early 2000. The result was a noticeable improvement in well delivery time, and significant drilling cost reduction for the project. Today, few years after inception, the system has gained wide acceptance and its application has resulted in numerous runs on several projects for these operators, with each reporting marked improvement in drilling performance and significant associated cost reduction. This paper details application of the tool in solving complex field directional drilling problems, ranging from penetration rates to drillability beyond the scope of the conventional mud motor in the Niger Delta.
Improvement modules to the tools facilitated by field experiences and the future of the technology are also discussed.
Estimating Drilling-Induced Formation Damage Using Reservoir Simulation to Screen Underbalanced Drilling Candidates
Authors: Biswas Deepankar , Suryanarayana P. V. 
Published: December 2007

Abstract
In this paper, we illustrate an approach to underbalanced drilling (UBD) candidate selection based on damage assessment and characterization using dynamic reservoir simulations. A 2-phase, 2-dimensional transient reservoir simulator (eRes UBD) using a control volume finite element approach is used to reflect the reservoir conditions. Because of its unstructured grid formulation, the simulator is ideally suited for investigating near-wellbore phenomena, such as drilling-induced invasive damage. In addition, the simulator is augmented to capture dynamic formation exposure, thus enabling drill-ahead capability. Overbalanced drilling conditions are mimicked using the drill-ahead capability of the simulator by specifying an arbitrary depth-vs-time profile, and the resulting formation fluid distribution is investigated, with specific attention to near-wellbore saturation. The impact of invasive damage on productivity is then examined by putting the well into production. Additionally, the extent of damage, flowback period and return permeability are characterized through perturbing critical reservoir and fluid variables. Representative sector simulation runs exhibit the longer term benefits of UBD as compared to conventional counterparts. The methodology described in the paper can ultimately guide the screening and selection of UBD candidates, and is an important part of value-based selection of UBD candidates.
New Tools for Fracture Design Optimization
Authors: Oberwinkler Christian , Ruthammer Gerhard , Zangl Georg , Economides Michael J. 
Published: December 2007

Abstract
Designing an effective and optimum fracture treatment is a complex and time-consuming task, especially in the case of new fields where the number of unknown variables is much larger than the number of known variables. Even with growing field maturity, changes in the fracture design often tend to be marginal and do not lead to a drastic improvement in the fracture design manifested by the post fracture production. This is not say that even marginal treatments are economically unattractive. Fracturing even when done badly is still one of the most economically rewarding petroleum operations. What we are addressing is a much more advanced and refined approach to design where economic benefits can be doubled or tripled.
One explanation for the absence of continuous improvement of fracture treatments is lack of the appropriate tools to perform a thorough data-mining task, which would lead to a definitive improvement in post fracture production benefits.
The appropriate tools for this task are presented in this paper. Although these tools are commonly used in other industries, they are still relatively new to most petroleum engineers.
This paper provides an introduction to the technology and procedures to mine large databases for hidden, but valuable underlying relationships.
An included comprehensive case study presents the workflow of the data mining approach to fracture optimization.
A combination of Neural Networks and Genetic Algorithms, both regarded as artificial intelligence tools, are first applied to the data.
The Neural Network is trained on historic data and captures the relationship between a certain data set of input parameters and the corresponding output parameter. This relationship is stored in the architecture of the Neural Network.
In a following step, the Neural Network is used by the Genetic Algorithm optimization tool to calculate the optimum values for the various input parameters: in this case to maximize the output – the production after fracture treatment. Genetic algorithms are inspired by Darwin's law for the survival of the fittest. For the particular case the fittest values for the different parameter are those, which generate a high post fracture production.
The results are than verified with the Unified Fracture Design approach. Neural Networks use historic data to train. It is required that the data show significant variation to capture the relationships between input and output. Data sets, which show too low variation in production (mainly on the poor side), cannot be optimized based on the artificial intelligence approach. For this case data mining results are integrated into the Unified Fracture Design approach, which will point to the optimum design.
The combination of data mining with an appropriate fracture optimization design approach is a powerful combination in production engineering and one assured to provide large incremental economic benefits to the industry.
Analysis of Off-Balance Fracture Extension and Fall-Off Pressures
Authors: Daneshy Ali 
Published: December 2007

Proposal
Three different techniques are presented for detection of the presence and severity of off-balance fracture growth. These are statistical analysis of total friction pressure during mini-fracs, analysis of mini-frac shut-in data, and statistical analysis of main treatment pressures. Most treatments allow application of all these techniques, which will increase the level of confidence in the analysis. All these techniques rely mainly on changes in treatment pressure, not its absolute value. This makes them very suitable for analysis of majority of industrial hydraulic fractures.
Off-balance growth can result in breakage of the bond between the casing and formation. This condition is defined as pseudo-openhole and usually facilitates a better linkage between the wellbore and the dominant fracture, thus reducing the severity of off-balance growth.
Impact on Scale Management of the Engineered Depressurisation of Waterflooded Reservoirs: Risk Assessment Principles and Case Study
Authors: Chekani M. , Mackay E. J. 
Published: December 2007

Abstract
Increased oil and particularly gas production may be achieved in waterflooded reservoirs by stopping further water injection, and depressurising the reservoir to release solution gas.Pressure depletion may be accelerated by back producing injected brines.However, there is the possibility that these brines may cause formation damage by mobilising fines or deposition of inorganic scales.Scale deposition in production wells may also occur as a result of pressure depletion, with calcite scales being precipitated when the system drops below the CO2 bubble point pressure.This paper discusses the assessment and prediction of scale related formation damage problems that are likely to occur during depressurisation of a case study field.The potential for the specific problem arises from the formation of barium sulphate scale as a result of mixing of injected and formation brines during production.Data used in this study includes well brine chemistries and an existing finite difference reservoir simulation model of the field depressurisation, which was used to calculate the mixing of injected and formation brines, and the movement of the mixing and temperature fronts during waterflooding and subsequent depressurisation.
This study has determined that the behaviour of the scaling potential for each well in this field is different.Also, the degree of scaling, both deep within the reservoir where it does the least damage, and around the wellbore (for both injectors and producers) where it may adversely affect production, can be predicted by detailed modelling using both conventional and reaction-flow simulations.Former injectors converted to water production or infill wells drilled in the aquifer for pressure depletion may experience an increase in the scaling potential that significantly impacts the economics of the project because of the need for extensive prevention (inhibition) treatments.The increased scaling potential in these wells is a result of the dynamics of brine mixing in the reservoir, the lowering of reservoir temperature in the vicinity of injection wells during waterflooding, and the large volumes of water that require to be produced to achieve depressurisation.The magnitude of the scaling problem and the economic impact are lower for the production wells due to lower water production rates and higher temperatures.
Scale Control Within North Sea Chalk/Limestone Reservoirs. The Challenge of Understanding and Optimizing Chemical Placement Methods and Retention Mechanism: - Laboratory to Field
Authors: Jordan M. M. , Sjursaether K. , Collins I. R. 
Published: December 2007

Abstract
The scale control challenges for two North Sea carbonate reservoirs are reviewed in this paper. Whilst carbonate reservoir are not the largest source of hydrocarbon within the North Sea, they are very significant on a global bases.
The mechanism of scale inhibitor chemical retention observed for phosphonate, polymer, and vinyl sulphonate co-polymer inhibitors on carbonate reservoir substrates is outlined. Chemical placement represents the most significant technical challenge when performing scale squeeze treatments into fractured chalk reservoirs. Examples from over 50 field treatments applied in reservoirs E and V, where both phosphonate and vinyl sulphonate polymer chemicals have been deployed, are used to illustrate the difference in chemical retention observed in laboratory evaluations. The laboratory studies demonstrated clear potential for significant extension in treatment lifetime by changing from a phosphonate to a vinyl sulphonate co-polymer-based scale inhibitor. The selection and qualification of chemical placement systems for deployment of inhibitors in fractured carbonate reservoirs are also outlined. To this end, novel technologies to enhance conventional scale inhibitor chemical placement are vital to economic success during water flood projects.
Acid Fracturing With Encapsulated Citric Acid
Authors: Burgos Gerardo , Birch George , Buijse Marten 
Published: December 2007

Abstract
The paper evaluates the design considerations and execution results of the first commercial field trial of a novel acid fracturing technique, using encapsulated citric acid as the etching agent. The treatment was executed in the Maraca tight carbonate oil reservoir (16,000 ft, 270°F) under Lake Maracaibo, Venezuela. The main driver for this trial with an alternative acid was to obtain a significant increase in etched fracture length, over the current standard acid formulation for this reservoir of acetic and formic acid. The encapsulated citric acid is solid at temperatures up to 180°F and coated with vegetable oil to avoid dissolution in the carrier fluid. The job was designed for a target etched half-length in excess of 300 ft. The job was an operational success, placing 30,000 lbs of the solid acid in the formation. Post-treatment results, however, did not show any improvement in production from the test well. The paper also reviews several of the possibilities for the failure of the treatment and the limitations of the technology as an effective acid for fracturing carbonate formations.
Model for Displacement of Herschel-Bulkley Non-Newtonian Fluid by Newtonian Fluid in Porous Media and Its Application in Fracturing Fluid Cleanup
Authors: Yi X. 
Published: December 2007

Abstract
Recent laboratory and field studies performed by oil and gas service companies indicate that fracturing polymer may exhibit yield stress after water leak-off. Its rheology may be described by Herschel-Bulkley model. It is reported in the literature that yield stress might be responsible for low fracturing fluid cleanup efficiency. In this paper, we derive an extended analytical Buckley-Leverett type model for the displacement of non-Newtonian Herschel-Bukley fluid (e.g. fracturing fluid) by Newtonian fluid (e.g. hydrocarbon/water). Using this model, we study the effect of yield stress and other rheological parameters on fracturing fluid displacement efficiency. Parametric analysis indicates that high values of yield stress τ0, consistency index K’ and flow behavior index n’ lead to low displacement efficiency. It is found that, for a given set of relative permeabilities, if a pressure gradient is not enough to overcome a critical pressure gradient, non-Newtonian fracturing fluid will not flow and only Newtonian fluid will be produced. It is demonstrated that low displacement efficiency can be overcomed by increasing displacing rate.