bluuebunny/crossref_metadata_2025 huggingface dataset:
Multistage Hydraulic Fracturing in an Openhole Ultratight Sandstone Formation in China—Design Considerations and Execution Results
Authors: Zhou Zongqiang , Li Xianwen , Xu Yonggao , Chong King Kwee , Marshall Eric Jonathan , Zhang BaoNan
Published: December 2007

In the winter of 2005, the first multistage completion in an openhole, ultratight sandstone reservoir of the Dot Three field, China, was successfully completed using hydrajet-fracturing technique. Six propped hydraulic fractures were placed individually at strategically selected locations along two horizontal wellbores.

Many horizontal wells with openhole completions have been drilled in low-permeability sandstone formations. The Dot-Three reservoir is one such case. Many of these wells perform below predicted rates with uneconomical oil production. Until recently, no method existed to effectively fracture-stimulate this type of horizontal, openhole wellbore to optimize production.

Successful proppant placement in the Dot Three field (this field has adopted early-c waterflood pattern) has proved to be extremely difficult in the past. Propped fracture treatments pumped within the past 10 years were not successful and their post-frac production only averaged 1 ton oil/day. Proppant placement problems occurred, and were believed to be caused by simultaneous propagation of very narrow multiple hydraulic fractures.

Past propped fracture treatments were performed on vertical wells and a few multiple fracture treatments on horizontal wellbores. These were only possible inside a cased hole using conventional methods (i.e. perforate, frac, set mechanical/chemical zone isolation, repeat cycle). The resulting treatment efficiency was low and results were not satisfactory.

Because successful development of this reservoir would significantly impact Chinese oil production, another method for fracturing cased, horizontal wellbores and a new method of propped fracture stimulation in horizontal, openhole wellbores was justified.

This paper discusses a hydrajet-fracturing technique that uses dynamic fluid energy (instead of mechanical methods) to isolate treatment fluid flow to a specific fracture point along the wellbore. Final results compared to past fractures using conventional methods and post-fracture production responses of the two experiment wells are also discussed.
Injection Profiling in Polymer Injectors in Daqing Oilfield
Authors: Zheng H. , Liu X.-B.
Published: December 2007

Daqing oilfield is implementing large-scale polymer flooding to increase oil recovery. With the increasing of injection fluid viscosity, some traditional injection profiling methods lost their validity. Three methods developed for polymer injection profiling have been used in Daqing oilfield.

An electromagnetic flowmeter was designed for water/polymer injection profiling in injectors without separate-zone injection mandrel at zones. It can survey in both continuous and stationary modes. It is verified that the logging tool string also works perfectly in Alkaline/Surfactant/Polymer injectors. It has been successfully applied more than 2400 runs for polymer injection profiling.

Oxygen activation tools have been applied for measuring water or polymer flow behind tubing and even casing. The logging tool widely used in Daqing oilfield consists of casing collar locater, a neutron generator, three gamma-ray detectors, and relevant circuits. Its measurement error is less than 5 % in the flowrate range from 20 m3/d (130 B/D) to 400 m3/d (2520 B/D) of flow in the annular space between 73 mm (2-7/8 in) OD tubing and 140 mm (5-1/2 in) OD casing. It is applied 350 runs each year, including 250 runs for polymer injection profiling.

Tracer logging with correlation arithmetic has been applied more than 500 times in polymer injectors. The method utilizes gamma-ray detectors to measure flow velocity after a slug of radioactive tracer has been ejected into borehole. The method is preferred for low-injection separate-zone polymer injectors.

Experimental results and field examples have proved that electromagnetic flowmeter, oxygen activation tool, and tracer logging with correlation arithmetic are suitable for polymer injection profiling in Daqing oilfield.
Validation of a 16-in. Bulk Meter for Allocation Metering
Authors: Al-Sibani Salim , Sequeira Daniel
Published: December 2007

The use of Coriolis based mass flow meters and turbine meters is well known in the oil industry for measurement of bulk fluids (two and three phase) exported from their central processing facilities. Large flow rates and the presences of gas in the flow affect the measurement accuracy and performance of these meters.

A typical solution for the same is to use a large sized three phase multiphase meter as done by PDO in its Amal field. This is one of the first deployments of its kind anywhere in the industry. PDO is pleased to jointly present here with its vendor, Haimo, the results of a verification process that has been carried out on one of its large size multiphase meters capable of handling between 15,000 m3/day to 57,000 m3/day (approx. 90,000 bpd to 340,000 bpd) with a GVF from 0 to 50% (Fig. 3)

The results have produced some impressive comparisons. The presentation shall result in communicating the following to the end users:

Application of Bulk Meter for export flow measurement and allocation metering. Another way of verifying the individual well test meters against an export reference, especially where there are no references available in form of test separators, meter provers or the like.

This paper is a summary of methodology used and the results obtained. It is only a factual representation of the data obtained with some additional analysis as carried out by PDO and its vendor.
The Reliability Problem Related to Directional Survey Data
Authors: Ekseth Roger , Kovalenko Kazimir , Weston J. L. , Torkildsen Torgeir , Nyrnes Erik , Brooks Andrew , Wilson Henry
Published: December 2007

The validity of error model predictions of wellbore position accuracy is highly dependent on the application of rigorous quality control procedures to the survey data. Concern has been expressed within the SPE Wellbore Positioning Technical Section (WPTS, formerly ISCWSA) that failure to apply the necessary operational procedures may be commonplace, raising questions about the reliability of the survey data so generated. Directional survey data that does not conform to its model’s predictions represents a risk in terms of lost production, damage to infrastructure and loss of life.

This paper lists all sources of error, describes internal data checks that are capable of identifying many of them, and highlights those that are missed and which will therefore require alternative QC measures. Real wellbore survey data are used to illustrate how the use of inadequate QC procedures can lead to invalid survey data being accepted as valid.

The paper is the product of collaborative work within the SPE WPTS.
Gas to Wire (GTW) System for Developing "Small Gas Field" and Exploiting "Associated Gas"
Authors: Watanabe T. , Inoue H. , Horitsugi M. , Oya S.
Published: December 2007

A new development concept of marginal gas field and associated gas with a reserve between 10 bcf and 1 tcf is suggested. This concept is called as a Gas to Wire System (GTW), which means onsite power generation by produced gas. Because of no need of transportation of the produced gas, GTW is considered to be high efficiency system with merits from economic and environmental perspective.

Japan Oil, Gas and Metals National Corporation (JOGMEC), Hitachi, Ltd., JGC Corporation, Toyohashi University of Technology, and Arabian Oil Company have advanced the research project on high efficiency of totally 50 % thermal efficiency, low cost and low emission GTW by applying Gas Turbine Combined Cycle System (GTCC). The targets of this project are (1) the development of the new burner which is available both gas and oil (NOx emission <25 ppm for gas, <80ppm for oil/oil + gas, and combustion efficiency >99.9%), (2) the design of the low cost pre-treatment for fuel. The technology (1) would add the cost value of the generator itself and give the GTW system the back-up fuel.

The test facility for the technology (1) was prepared and the design and construction of small model burners was carried out. The result of small model burner test shows low NOx emission for both oil and gas. Investigation of particulate material/soot formation affected by fuel properties and impurities was carried out. Corrosion test equipments were designed and constructed. Process flow of available treatment equipments was composed with consideration for impurities permission levels for gas turbine as the technology (2). The tentative feasibility study was carried out. It shows that GTW system makes a marginal gas field valuable and has less power loss from well to GTCC. The subjects in near future are achievement of each target for the developments, conceptual design of GTW system for selected gas field and the assessment of economical feasibility.
Managed-Pressure Drilling – Recent Experience, Potential Efficiency Gains, and Future Opportunities
Authors: Kozicz John
Published: December 2007

Recent development of Managed Pressure Drilling (MPD) Techniques for use from floating drilling rigs began in the late 1990’s concurrent with the development of 5th generation offshore drilling vessels(1). During this period a number of industry efforts focused on developing "riserless" or dual gradient drilling systems employing subsea mu d return pumping system. One of these efforts(2) culminated with the drilling of a test well in the Gulf of Mexico employing a subsea pump based Dual Gradient drilling method. Additionally, during this period another industry group employed aerated drilling fluid and a closed loop circulating system to drill a pressure depleted well section offshore Brazil from a floating drilling rig (3). While technically successful, these efforts did not result in commercially deployable drilling systems.

Much of the initial industry focus has been on developing MPD methods for deepwater applications, many of the techniques are applicable to all offshore drilling operations and a number of recent applications of Constant Bottom Hole Pressure drilling methods have been employed from fixed installation in both the North Sea and US GOM (4, 5, 6). At the same time both Surface BOP and RiserCap™ equipment configurations (Fig 1) have been employed to implement Pressured Mud Cap Drilling from floating drilling rigs offshore South East Asia.
Intelligent Drilling: A Prospective Technology of Tomorrow
Authors: Hu Qin , Liu Qingyou
Published: December 2007

The system composition, function, and run mode of a new intelligent drilling technology in future are prospected in this paper. The technologies, including drilling, new materials, detection controls, microelectronics, telecommunications, computers, robots and ultramicrotechnique, etc., are integrated into the new intelligent drilling technology in future. The portable, truck-mounted, flexible and full automatic drilling rig with coiled tubing will be employed in this system. In future drilling process, intelligent mini-robots mounted on the drill bit will be used to observe and detect all the downhole parameters and send them back to ground so as to simultaneously finish the logging operation in drilling process; intelligent drilling under remote control will be realized by means of controlling the drilling speed and trajectory of bit; all the drilling operations, such as tripping operation, will be completed automatically by the ground robots according to instructions; the cooperation among global drilling operations will be organized through communication network technology. Therefore, it is anticipated to significantly increase the drilling speed with greatly reduced drilling accidents and cost. Owing to the realization of precise control over well trajectory, the intelligent drilling technology will improve the exploration and development of petroleum and natural gas.
Computing Gas in Place in a Complex Volcanic Reservoir in China
Authors: Li GuoXin , Wang YuHua , Yang FengPing , Zhao Jie , Meisenhelder Jeff , Neville Thomas J. , Farag Sherif , Yang XingWang , Zhu YouQing , Luthi Stefan , Hou HuiJun , Zhang ShuPin , Wu Chuan , Wu JieHui , Conefrey Michael
Published: December 2007

Gas-bearing reservoirs of the YingCheng Group in the SongLiao Basin in northeastern China are hosted in a complex assemblage of volcanic rocks. These reservoirs present a large number of interpretation challenges that have made the evaluation of gas-in-place (GIP) problematic. A fit-for-purpose workflow was developed for one accumulation in this area to provide robust GIP estimates in support of a development decision.

The workflow involves a number of novel techniques developed to address the challenges presented by these reservoirs. Rock typing was conducted through integration of core descriptions with neutron capture spectroscopy, nuclear magnetic resonance logs, and borehole images using a neural network approach. These rock types, characterizing variations in chemistry and rock texture, were then propagated in a geocellular model using multivariate seismic attribute analysis and distribution rules based on volcanic analogues. Porosity and water saturation from an innovative petrophysical interpretation methodology were propagated throughout the model based on these rock types. The distribution of both rock types and petrophysical properties was performed stochastically and a range of potential GIP estimates was developed.
Paraffin Deposition Problems of Mumbai High
Authors: Nagar A. , Mangla V. K. , Singh S. P. , Kachari J.
Published: December 2007

Mumbai High located about 160 km West–North-West of Mumbai city in the Arabian sea on the continental shelf of Western India, is the largest and most prolific oil field in India. It is divided into two blocks i.e. North and South. Two important carbonate reservoirs in Mumbai High are L-II & LIII. In between these two blocks L-III reservoir becomes shaly, which acts as a barrier between these two blocks facilitating independent exploitation of the reserves of Mumbai High North and South fields. The clastic reservoir S-1 sand is free gas bearing and it lies in between L-II & L-III reservoirs. L-III reservoir which is present through out the field while L-II reservoir is hydrocarbon bearing only in the Northern block of Mumbai High. The L-III reservoir is multilayered accumulation with 10 main sub layers. The sub layers are designated from top to bottom as A1,A2-I to A2-VII,B & C. Crude oil in A1 layer in western flank is highly paraffinic in nature having high pour point, wax content & asphaltenes. The wells producing waxy crude oil from A1 layer in western flank have shown gradual decline in production due to precipitation and deposition of paraffins & asphaltenes causing impairment of permeability. Deposition of asphaltene in the reservoir makes the formation oil wet there by reducing the relative permeability to oil. Asphaltenes are not soluble in straight chain hydrocarbons such as Kerosene, Diesel oil and Condensate. A new chemical formulation was developed which was field implemented.

The treatment has improved the well productivity of number of wells. The best part of the technique is the sustained production. Case studies of number of wells has been discussed in the paper.
Formation Pressure Testing while Drilling in Bohai Bay's Challenging Environment
Authors: Hahne Ulrich , Pragt Jos , Venier Martin , Meister Matthias , Tan Jenson , Chunsen Dai
Published: December 2007

This paper describes the experience and lessons learned to acquire logging while drilling (LWD) formation pressure and near-wellbore mobility data in Bohai Bay. This area is known to be difficult in terms of measuring key parameters for reservoir description in conventional wireline logging (WL) programs.

While comparisons between WL and LWD, including costs savings associated with the LWD approach, are common today in operators’ minds, the intangible benefits gained by real-time acquisition of these critical data are often neglected. Incorporating formation pressure testing into the drilling process, on the other hand, creates challenges to perform measurements in a timely manner as well as the need for continuous circulation while testing to ensure wellbore safety.

Formation testing at Bohai Bay is difficult because of the unconsolidated formations and all aspects associated with this type of environment, such as borehole stability, hole washouts, sanding while testing, or lost seals.

This paper describes successful test procedures, like the orientation of the probe into any direction, and discusses test examples from various hole sizes in detail. The key to achieve a high sealing success rate seems to be the ability to control and adjust the pad contact forces against the formation. Analyzing each drawdown sequence in the tool downhole and optimizing the drawdown rate and speed in the consecutive test reduces effects like sanding and improves the overall success rate.

Providing this type of formation evaluation data with an LWD tool allows a continuous approach to data evaluation and decision-making. The ability to measure accurate LWD formation pressure data in a variety of hole sizes represents a significant opportunity for safe and cost-efficient wellbore construction, especially in environments like Bohai Bay.
Preventing Mud Losses and Differential Sticking by Altering Effective Stress of Depleted Sands
Authors: Benaissa Saddok , Bachelot Alain , Ong Seehong
Published: December 2007

Drilling through highly depleted sands can result in a multitude of problems such as lost returns, differential sticking, difficult logging and/or not being able to reach the target depth. Often curing lost circulation can be difficult and costly as a result of associated nonproductive time and escalating mud costs. Remedies such as cement plugs, squeezes, expandable liner and casing while drilling can be costly solutions and are not always successful.

The use of fluid management techniques, team efforts and proper engineering have lead to the development of an innovative approach to prevent problems and avoid the complex processes of curing mud losses and freeing stuck pipe.

A newly developed deformable sealing agent can be added to a water-based fluid at 2 to 4% volume. It is a modified liquid insoluble polymer that is designed to reduce pore pressure transmission by internally bridging the pore throats of the low permeability sands and shale micro-fractures. These bridging and sealing characteristics will help protect the formation where lost circulation may be encountered. This effective bridging enhances the effective rock strength, hence increasing the formation fracturing resistance.

A geomechanical analysis indicates that two mechanisms contribute to the success: (1) The near wellbore region is turned into an altered rock because the particles in the new mud tend to block the pore spaces. Stress analyses using rock mechanics theory indicate that fracturing pressure is increased by increasing the tangential stress around the borehole resulting from the ‘enhanced’ mechanical properties of the altered zone. (2) Because of this blockage, it is envisaged that the near wellbore rock strength is increased. This strengthening effect increases the bulk and tensile strengths of the altered rock and increases the fracturing pressure.

This paper will highlight field case histories supported by preliminary laboratory work and geomechanical studies indicate that mud losses associated with severely depleted tight sands can be reduced with the use of the newly developed deformable sealing technology. Some of the field accomplishments of this "internal mud cake" as a bridging/sealing approach are: improved drilling curve, lower well cost, stable and gauge hole, reduction in mud losses and differential sticking and reduction in NPT
Effect of Formation Modulus Contrast on Hydraulic Fracture Height Containment
Authors: Gu Hongren , Siebrits Eduard
Published: December 2007

Much study has been conducted on the effects of formation Young's modulus and in situ stress on hydraulic fracture height containment in layered formations. It has been well documented that in situ stress contrast is the dominant parameter controlling fracture height growth and that Young's modulus contrast is less important. However, a recent study pointed out that modulus contrast can have significant implications on fracture geometry and proppant placement.1 To expand on this topic further, we consider the combined effects of modulus contrast and in situ stress contrast on fracture geometry. A pseudo 3D (P3D) hydraulic fracture simulator with a rigorous layered modulus formulation is used in this study. The fracture height calculated based on uniform modulus versus layered modulus, under the same in situ stress contrast conditions, is compared.

The results are analyzed and explained, based on fracture mechanics fundamentals as well as the coupled fluid pressure effect in hydraulic fracturing. One important finding is that fracture height can also be contained by low modulus layers. The results from this study can be applied to hydraulic fracturing treatments in formations with moderate to significant modulus contrast. The mechanisms studied in this work could also partially explain some recent results from microseismic or tiltmeter mapping that show more fracture height containment than that predicted by commonly used P3D hydraulic fracturing simulators based on averaged modulus.
New Trend in Oilfield Flow Assurance Management: A Review of Thermal Insulating Fluids
Authors: Wang Xiaolan , Qu Qi , Javora Paul , Pearcy Rick
Published: December 2007

Flow assurance has been one of the major considerations in deep water completion design, where undesired heat loss from production tubing contributes to the formation of gas hydrates and causes the deposition of paraffin and asphaltene materials. Traditionally, controlling annular heat loss has been achieved with the injection of steam, the application of silicate foam, the pressurization of the annulus with inert gas, the use of gelled oil as an insulating packer fluid, and the use of vacuum insulated tubing (VIT). Each of these applications, however, has drawbacks due to either its working mechanism or higher cost associated with the technology.

To secure the insulation of the wellbore and to reduce heat transfer from the production tubing to the surrounding areas, various aqueous insulating fluid systems with superior thermal properties have been developed in recent years. Field applications of these fluids have demonstrated significant reduction in heat loss by reducing conduction and minimizing convection. These thermal insulating fluids have been implemented with great success in over 75 deepwater riser and packer applications in the Gulf of Mexico (GOM) over the last several years. Case histories have demonstrated that installation of these water-based insulating fluids is an effective alternative to conventional insulation options, and is becoming the preferred insulation method in many deepwater projects.

This paper will highlight the evolution of different insulating fluid systems and the field experience with each system. Proper testing methods relevant to oilfield flow assurance will be discussed and testing results for these fluids will be detailed. Field cases in the Gulf of Mexico (GOM) will be summarized and the effectiveness of these fluid systems will be demonstrated.
Optimal Strategy of Disposing of Mercury-Contaminated Waste
Authors: Rangponsumrit Manisa , Athichanagorn Suwat , Chaianansutcharit Thotsaphon
Published: December 2007

Mercury contaminated waste is one of the byproducts from hydrocarbon production in many gas fields in the Gulf of Thailand. One method to dispose the toxic waste is to inject mercury contaminated waste into confined depleted reservoirs through a depleted well. The advantages of this approach are high disposal capacity and permanent waste elimination. In the selected field of this study, the most suitable structure which is confined and in the last stage of production, was chosen. Since the selected reservoirs are not completely depleted, gas should first be produced. Thus, there is a need to optimize both the production and waste disposal strategy. In this study, a 3D reservoir simulator is used to determine strategy, which maximizes gas production and mercury contaminated waste disposal.

The reservoir simulation model for the reservoirs in the chosen compartment was constructed from seismic, well log, and special core analysis data. Initial reservoir conditions and fluid properties were entered into the model, and history matching on production performance and reservoir pressure was performed to fine tune the reservoir model. Then, reservoir simulation was performed to optimize hydrocarbon production by varying perforation plan and production gas rate. Finally, mercury contaminated slurry injection was optimized by performing sensitivity simulation on slurry density, injection rate, and slurry viscosity. The effect of these parameters on injection capability was also investigated. The optimal injection criterion is minimum injection time under a condition that the injection pressure is not high enough to create any fracture in the reservoirs.
Multistage Approach on Pore Pressure Prediction—A Case Study in South China Sea
Authors: Xie Yuhong , Cao Shunhua , Liu Chang , Yan Gongrui , Yi Ping , Cai Jun , Xu Liqiang
Published: December 2007

A multistage approach on pore pressure prediction was successfully used for a drilling program in the South China Sea. The objectives were to optimize the casing-shoe position by predicting the overpressure profile in the formation and to select the optimal mud weight by forecasting the formation pressure variation.

Before spudding the well, data from a surface seismic survey and log data from a nearby well were collected to build a pore pressure uncertainty model. This initial model had a pore pressure profile with relatively large uncertainties. While drilling, the model was updated in stages with additional measurements, such as those derived from vertical seismic profiles (VSPs), dipole sonic logs, gamma ray (GR) logs, etc. These additional data significantly reduced the uncertainty of pore pressure estimation.

At each intermediate total depth (TD), wireline logs and VSPs were acquired. Pore pressure profile above the current TD was estimated using the wireline logs and VSP velocity. Pore pressure profile below the current TD was estimated using the look-ahead VSP inversion result. Above the current TD, a cross-check validation was made by comparing the pore pressure profiles estimated from wireline logs and VSP data. The predicted pore pressure model was calibrated with the actual mud weight and a well integrity test at 3505 m.

At the well-planning stage, the maximum pore pressure was estimated to be 1.55 g/cm3. At intermediate drilling stages, the pore pressure was consistently estimated to be between 1.9 and 2.1 g/cm3 below a depth of 4100 m. This prediction was later confirmed by the formation test pressure value of 1.98 g/cm3 at 4226 m.

All pore pressure prediction results were delivered within six hours after each intermediate data acquisition. The pore pressure prediction results were successfully used for the critical decision of setting the casing shoe and selecting the mud weight.
Triaxial Induction Logging: Theory, Modeling, Inversion, and Interpretation
Authors: Wang Hanming , Barber Tom , Chen Kouchiang , Davydycheva Sofia , Frey Mark , Homan Dean , Minerbo Gerald , Morriss Chris , Rosthal Richard , Smits Jan , Tumbiolo Giovanni
Published: December 2007

Thinly laminated sand-shale formations represent a difficult challenge for petrophysical evaluation. The conductive shale laminations have a profound effect on the traditional induction log, causing it to read the shale laminations significantly lower than the high-resistivity sand layers. This misreading leads to pessimistic computations of water saturation and estimations of reserve. The newly developed triaxial induction logging tool provides much more information than the conventional induction logging measurement. It is not only sensitive to the effective horizontal resistivity, which is dominated by the conductive shale layers, but it is also sensitive to the effective vertical resistivity, which is determined by the conductive shale and the resistive sand, at any dip angle.

A key challenge of developing the triaxial induction array is the large borehole effect on coplanar couplings when the tool is eccentered in the transverse direction in water-base mud boreholes. To reduce the borehole effect to a manageable level, a new design with multiple electrodes has been implemented. Tank experiments and numerical modeling results show the borehole effect is reduced dramatically by using this design.

A parametric inversion algorithm to simultaneously determine the horizontal resistivity, vertical resistivity, formation dip, and azimuthal angle and bed boundary position from the triaxial induction logging data will be presented. The inversion problem is solved by employing a weighted, constrained, and regularized Gauss-Newton minimization scheme. To archive the practical application of the inversion algorithm, a fast Jacobian matrix computation is implemented to improve the efficiency. Furthermore, a multiplicative regularization technique is used to automatically determine the regularization coefficient. Synthetic examples will be presented to indicate the robustness of the algorithm.

A quantitative interpretation method of water saturation in laminated shale-sand formation will be presented. Shale anisotropy is taken into account for building the interpretation model. Two field examples demonstrate the laminated shale-sand analysis improves the estimate of hydrocarbons in place.
Efficient Field-Scale Simulation of Black Oil in a Naturally Fractured Reservoir via Discrete Fracture Networks and Homogenized Media
Authors: Li Liyong , Lee Seong H.
Published: December 2007

This paper describes a hybrid finite volume method, designed to simulate multi-phase flow in a field-scale naturally fractured reservoir. Lee et al. (WRR 37:443-455, 2001) developed a hierarchical approach in which the permeability contribution from short fractures is derived in an analytical expression and that from medium fractures is numerically solved using a boundary element method. The long fractures are modeled explicitly as major fluid conduits. Reservoirs with well-developed naturally fractures include many complex fracture networks that cannot be easily modeled by simple long fracture formulation and/or homogenized single continuity model. We thus propose a numerically efficient hybrid method in which small and medium fractures are modeled by effective permeability and large fractures are modeled by discrete fracture networks. A simple, systematic way is devised to calculate transport parameters between fracture networks and discretized, homogenized media. An efficient numerical algorithm is also devised to solve the dual system of fracture network and finite volume grid. Black oil formulation is implemented in the simulator to demonstrate practical applications of this hybrid finite volume method.
Old and Modern Well Log Data and Its Reliability Through a Novel Certification Process
Authors: Camacho V. R. , Lobato-Barradas G. , Campos S. Berumen , Daal A. , Martell B. , Adams D. , Cruz E. , Hernandez V.
Published: December 2007

The main objective of this paper is to present a certification process to achieve the reliability of well log data for any user, independently where or when the log was ran. For example, the analogical log data (old data) is digitally recaptured and processed through quality control criteria's, edited and spliced curve by curve, where all technical steps are documented in the corresponding digital file in order to provide the user the details of how the technical process was used and made. Finally, a digital signature certifies all files. At that moment anyone can use the certified products for interpretations, correlations or petrophysical evaluations.

As it is the case in most oil producing companies, two log data generation are present in Mexico: analogical and digital. Analogical process was initiated in 1904, when the first well was drilled, and the digital process began in 1979 through the "Cyber System Unit" used by Schlumberger. Those two generations, analogical and digital log data, demand new technologies and process to equalize the quality of old and modern data in order to use and manage this information in applications and databases.

The certification process includes on line log inventory using the log and services codification published by The American Petroleum Institute (API), log quality control routine for "Digital Log Interchange Standard" (DLIS), "Log Information Standard" (LIS) and "Log ASII Standard" (LAS), including: originals, edited and spliced logs. The authenticity and reliability of each file is warranted by a digital signature, it specifies who made the process and who accepted the final product.

The certification process was designed to equalize the quality of analogical and digital log generations, to establish the log reliability for any user and, finally to improve the data management. All these factors impact positively log data base preparation for project execution.
Optimize Drilling and Reduce Casing Strings Using Remote Real-Time Well Hydraulic Monitoring
Authors: Tollefsen E. , Goobie R. B. , Noeth S. , Sayers C. , Boer L. den , Hooyman P. , Akinniranye G. , Cooke J. , Thomas R. , Carter E.
Published: December 2007

Remote real-time pore pressure monitoring using a combination of Logging-While-Drilling (LWD) services coupled with a predrill pore-pressure model provides significant insight into wellbore stability and allows for optimizing casing points. This paper presents the results of a job in the Gulf of Mexico (GoM) that allowed an operator to drill confidently in a very tight hydraulic envelope and eliminate a string of casing.

The real-time use of data from the LWD formation pressure and sonic tools provides confidence in geopressure predictions. These LWD measurements allow the predrill velocity-to-pore-pressure transforms established during predrill modeling to be updated while drilling using the velocities from the sonic tool and pressures from the LWD formation pressure tool. This calibrated transform is then applied to revise the predrill pore-pressure model while drilling, thus reducing the uncertainty in the pore-pressure prediction ahead of the bit. In this case, the predrill model used velocities extracted from a 3D mechanical earth model of the northern GoM based on velocities derived from checkshots and sonic logs. These velocity data are kriged to give a 3D velocity model with uncertainty estimates.

Using state of the art Logging-While-Drilling (LWD) technologies, a new methodology was initiated to optimize drilling performance on a Vermillion 338 well. Continuously updated LWD annular pressure measurements effectively gauge wellbore pressures and help the driller rapidly intervene in pressure and/or geomechanical wellbore stability issues. A complete understanding of the hydraulic forces on a borehole can increase the rate of penetration, provide greater safety, minimize casing strings, reduce or eliminate kicks and formation fracturing, and allow faster and less expensive completions.

The technique described in this paper allows for incorporating real-time measurements into a pre-drill model, thus reducing the uncertainty ahead of the bit and allowing the operator to extend both the 9-5/8-in. intermediate casing and 7-in. liner to TD. As a result, a critical casing string was pushed 1,287 ft deeper than planned and a pre-planned 5-in. liner eliminated. The reduction in casing expense, as well as slim-hole drilling and completion costs resulted in a savings to the operator of approximately $1.7 million.
Feasibility Study of In-Situ Combustion in Naturally Fractured Heavy Oil Reservoirs
Authors: Tabasinejad F. , Karrat R. , Vossoughi S.
Published: December 2007

In-situ combustion is a thermal recovery method used for enhanced heavy oil recovery. In this process air is injected to the reservoir in order to achieve ignition and to maintain the combustion front while pushing the heated oil toward producing wells.

This study deals with the feasibility of in-situ combustion process in fractured heavy oil reservoirs. A one dimensional, three-phase in-situ combustion simulator with six components, two cracking and three oxidation reactions is used in this study.

Primarily, a conventional simulation model based on experimental data available in the literature was constructed and sensitivity study tests were performed. In the second part of this project, the conventional model was modified to a fractured model and various parameters and mechanisms such as oil recovery factor, average temperature of the system, cumulative oil and water production, diffusion, and wet combustion process were investigated.

Results indicate the importance of grid block size, injection rates, kinetic models, and equilibrium ratios of heavy and light oil components on simulation process. Simulation results indicate that the optimum water/oil ratio leads to an increase in the amount of oil recovery and a reduction in the amount of air to be injected.

The study presented here with its promising outcome is a pre-requisite to justify laboratory experimental investigation of the in-situ combustion process in naturally fractured reservoirs.
Drilling Waste Management: Improvements to the Dewatering Process through Chemical Optimisation—Results of a Pilot Test
Authors: Mohammadi M. Kalhor , Almassi F. , Sampaio J. H. B. , Tahmasbi K.
Published: December 2007

Environmental legislation in Western Australia requires controls over the discharge of drilling wastes to preserve the natural environment. Nowadays, drilling operators use standard practices and treatments to reduce the drilling waste, which includes drilling fluids and wastewater.

Dewatering of the drilling fluids waste is one waste management practice that can help operators remain in compliance with environmental legislation. However, there are still some issues concerning the chemical cost and successfulness of the dewatering process. There is a clear incentive to reduce costs through optimum chemical selection, which, in turn, can lead to reduce equipment costs.

The primary objective of the research work reported here is to optimise the chemical consumption in the dewatering process. This has been achieved through a series of pilot tests carried out in the laboratory, and this paper describes the laboratory procedures employed to reach an optimum outcome. The procedures include the selection of the proper coagulants and flocculants by the common jar test method, and, in addition, the determination of the optimum chemical concentration by comparing the effectiveness of the dewatering process after centrifuge testing.
Design Criteria for Improved Performance of Fractured Wells
Authors: Poe B. D.
Published: December 2007

This paper presents the results of an investigation concerning the development of more accurate predictive and interpretive models of the boundary-dominated flow performance of vertically fractured wells located in closed rectangularly bounded reservoirs. In particular, improvements in the characterization of the dimensionless productivity index of vertically fractured wells in closed rectangularly bounded reservoirs during boundary-dominated flow have been made using a mathematically rigorous model for pseudosteady state flow. This model has been used to develop predictive and analysis graphical design charts of the dimensionless productivity index for improved fracture stimulation design and evaluation.

Other issues investigated in this work were the development of a general relationship for evaluating the pseudosteady state shape factor of a vertically fractured well in a closed rectangularly bounded reservoir, along with a review of appropriate applications of the apparent wellbore radius concept to vertically fractured wells in finite reservoirs. Example applications of the dimensionless productivity index and pseudosteady state shape factor solutions developed in this work are provided for fracture stimulation design.
Inflow Profiles Obtained With Pulsed Neutron Logs in Subcritical-Velocity Wells
Authors: Poe B. D. , Butsch R. J.
Published: December 2007

This paper addresses some recent developments in a production logging technique that uses Pulsed Neutron log measurements to evaluate the formation inflow into a wellbore, in which one or more of the completed intervals may be located in the annulus between the casing and tubing strings above the end of the tubing. Of particular importance in this work is the capability of determining the formation inflow profile in the well in cases where the well outflow velocity is less than that required to continuously transport and unload liquids from the well. Sub-critical velocities are commonly encountered in low productivity gas wells that produce liquids, whether they are produced directly from the formation and/or condensed well fluids, water and hydrocarbons.

This paper presents a sub-critical velocity analysis that has been implemented in a Pulsed Neutron production logging technique in order to have the capability to reliably evaluate the formation inflow into wells in which the velocities are so low that no other production logging methodology is possible. Coupled with the numerical modeling of the Pulsed Neutron production log evaluation, test pit measurements of the annular flow water velocities with the Pulsed Neutron logging technique have been reliably and accurately measured to as low as 3 ft/min (0.05 ft/s).
Characterization of Reservoir Properties Using Production Logs
Authors: Poe B. D. , Atwood W. K. , Kohring J. , Brook K.
Published: December 2007

This paper presents the results of an investigation involving the development of a reliable and accurate methodology for establishing the stabilized deliverability performance of multi-layer commingled reservoir systems using multi-rate production log measurements. Both linear and non-linear systems are considered in this work, providing a basis for the analysis of reservoirs that exhibit Darcy and non-Darcy flow, respectively.

An extension of the conventional Selective Inflow Performance analysis is presented in this paper to obtain estimates of the formation and well completion properties such as effective permeability, radial flow steady state damage/stimulation skin effect, and non-Darcy flow coefficient. In the specific case where the deliverability performance of a vertically fractured well is considered, estimates of the effective fracture half-length and average fracture conductivity may be derived from the analysis. In cases where the multi-rate deliverability measurements are obtained under boundary dominated flow conditions, conventional deliverability analysis techniques may also be employed to derive estimates of the reservoir drainage area in addition to the well and reservoir parameters that can be obtained in a transient flow analysis. Applications of the analyses reported in this paper demonstrate the use of the analyses for evaluation of the inflow performance of commingled multi-layer reservoirs using multi-rate production log measurements.
Determining Parameters of Matrix-Fracture Interface Fluid Transfer from Laboratory Tests
Authors: Civan F. , Rasmussen M. L.
Published: December 2007

Methodology is presented and proven for determination of the best estimate parameter values affecting the matrix-to-fracture interface fluid transfer in naturally fractured reservoirs. Improved matrix-fracture-transfer models are applied based on presumed matrix block shapes. Fracture surface hindered interface fluid transfer is considered between the matrix blocks and surrounding natural fractures. Analytical solutions developed for special boundary conditions are applied for the typical laboratory tests for rectangular and cylindrical shape rock samples. The workable equations and straight-line data plotting schemes are developed for effective analysis and interpretation of laboratory data obtained from various shape oil-saturated reservoir rock samples immersed into brine. This allows the rapid determination of the characteristic parameters of the matrix-fracture transfer models for various shape matrix blocks, which are essential for prediction of petroleum recovery from naturally fractured reservoirs by computer simulation. The methodology is verified using various experimental data concerning water imbibition into oil-bearing rock, and the values of the characteristic parameters, such as the diffusion coefficient, and skin coefficient and thickness, are determined.
Future Exploitation Strategy Using Integrated Subsurface-to-Surface Methodology: Field Case Study—Litoral De Tabasco Asset
Authors: Rosales A. , Barrera J. , Gonzalez L. E. , Martinez I.
Published: December 2007

In reservoir development studies or exploitation studies for a hydrocarbon producing field, it's necessary to go through different stages, from visualization to planning all involved activities. In visualization we must consider basic factors that will contribute to an optimal exploitation plan. Thus we need tools capable of integrating the whole system, from subsurface production all the way to the surface. Different subsurface productivity techniques, production methods, secondary recovery projects, facilities required, among others are the fundamental base for an adequate reservoir exploitation planning, considering all limitations within the system as well as related costs.

In this study, it's considered the analysis done for Field Exploitation for Litoral de Tabasco Asset (AILT), which comprises 14 hydrocarbon fields and all related production facilities of Region Marina Sur Oeste (RMSO). Different analysis techniques were applied such as: material balance (MB), nodal analysis (NA), simulation of multiphase gathering systems, statistics, integrating all this disciplines in a network to evaluate production scenarios for 15 years, considering production forecasts, pressure drops along the system and Asset production facilities limitations and needs. The integrated model will allow determining the optimal option according to the evaluated scenarios and facilities needs along the productive life of all analyzed fields.
Conformance While Fracturing: Technology Used to Reduce Water Production in North Mexico
Authors: Torres A. , Peano J. , Lopez E. , Ramirez R. , Dalrymple D.
Published: December 2007

Often, the main challenge in producing hydrocarbons in north Mexico is the accompanying large associated water production. In the Cuenca de Burgos field in northern Mexico, operators typically encounter water production of over 400 BWPD following fracture-stimulation treatments. This paper discusses how water production in those fields was significantly reduced using a new conformance-while-fracturing (CWF) method that incorporates a chemical relative permeability modifier (RPM) prepad.

The formations were reported to have high watersaturation levels. Fracture-stimulation treatments performed in similar intervals usually (1) intersected a stringer of water within the targeted interval, or (2) extended into the highly saturated areas above and/or below the interval. Water cuts as high as 50 to 60% had made production of such intervals uneconomical.

Data gathered from the first six months of production on more than seven wells in northern Mexico illustrate the economic benefit of the stimulation treatments using the new CWF technique. In many cases, the treatment has limited water production to less than 20%, and some applications have reduced water production to negligible levels. This paper discusses the job design, field application, and results of several CWF treatments performed in this area between 2004 and 2005.