bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of Surface and Shallow Microseismic Array for Deep Reservoir Monitoring
Authors: Rosca Anca , Maisons Christophe
Published: June 2014

Monitoring reservoir stimulation operations provides data for predicting production performance and for reservoir characterization but also, potentially, for compliance with local regulations. With improved drilling and completion technology the depth of the unconventional reservoirs produced increases and the options for deploying cost–effective microseismic monitoring equipment become limited. The monitoring technology has to adapt by optimizing acquisition geometry and data processing as well as the procedures that demonstrate the validity of the results. A practical solution for microseismic monitoring of stimulation operations in an unconventional reservoir under development is a surface or shallow distributed array. We are analyzing three such datasets together with complementary deep borehole sensor datasets to understand how to predict and validate the expected performance of distributed surface and shallow arrays. The surface recorded data is processed by stacking and event detection and location are accepted based on statistical criteria. This catalog of events is compared to the one obtained from borehole array where waveforms can be analyzed individually in order to validate the quality of event analysis.
Decision Criteria for Climate Projects
Authors: Osmundsen Petter , Emhjellen Magne
Published: June 2014

This article analyzes commercial decision criteria for climate projects. The latter will normally be executed by private players, for whom decision criteria developed from a commercial perspective are important. But such criteria are also important for the government in calculating the size of subsidies required for various measures. A ranking of different solutions in a socioeconomic context must rest on calculations made from a commercial perspective. Examples of the subjects covered include the calculation of abatement unit costs and cost estimating for climate projects. The carbon-capture project at the Kårstø gas-fired power station in southwest Norway is used as a case throughout the analysis.
Gel Dehydration by Spontaneous Imbibition of Brine From Aged Polymer Gel
Authors: Brattekås B. , Haugen Å. , Graue A. , Seright R. S.
Published: June 2014

This work investigates dehydration of polymer gel by capillary imbibition of water bound in gel into a strongly water-wet matrix. Polymer gel is a crosslinked-polymer solution of high water content, where water can leave the gel and propagate through porous media, whereas the large 3D polymer-gel structures cannot. In fractured reservoirs, polymer gel can be used for conformance control by reducing fracture conductivity. Dehydration of polymer gel by spontaneous imbibition (SI) contributes to shrinkage of the gel, which may open parts of the initially gel-filled fracture to flow and significantly reduce the pressure resistance of the gel treatment. SI of water bound in aged Cr(III)-acetate-hydrolized-polyacrcylamide (HPAM) gel was observed and quantified. Oil-saturated chalk-core plugs were submerged in gel, and the rate of SI was measured. Two boundary conditions were tested: all faces open (AFO) and two-end-open oil-water (TEO-OW), where one end was in contact with the imbibing fluid (gel or brine) and the other was in contact with oil. The rate of SI was significantly slower in gel compared with brine, and was highly sensitive to the ratio of matrix volume to surface open to flow, decreasing with increasing ratios. The presence of a dehydrated gel layer on the core surface lowered the rate of imbibition; continuous loss of water to the core increased the gel layer concentration and thus the barrier to flow between the core and fresh gel. Severe gel dehydration and shrinkage up to 99% were observed in the experiments, suggesting that gel treatments may lose efficiency over time in field applications where a potential for SI exists. The implications of gel dehydration by SI, and its relevance in field applications, are discussed for both gel and gelant field treatments.
Simulation of Fracturing Induced Formation Damage and Gas Production from Fractured Wells in Tight Gas Reservoirs
Authors: Ding Y. D. , Langouët H.. , Jeannin L..
Published: June 2014

Fracturing fluid may jeopardize the production of hydraulically fractured tight gas formations. Ascapillary forces are acting stronger in low permeable formation, the invaded fracturing fluid is harder to be removed. The increase of water saturation around the fractured well affects the mobility of the gas phase, particularly in tight formations where the gas relative permeability declines stronglywhen water saturation increases. This damage might greatly reduce the gas production in a very long cleanup period. This paper presents numerical simulation techniques to account for formation damage with both a near-well model and a full-field model for fractured wells in tight formations and to integrate damage effects in a full-field reservoir model through an efficient coupled modelling.
Wellbore Pressure Surges Produced by Pipe Movement
Authors: Burkhardt J.A.
Published: June 2014

Field measurements and theoretical studies have been made of pressure surges-momentary variations in fluid pressure-produced by movement of pipe in mud filled boreholes. Pressure measurements were recorded by five pressure gauges located at various positions in the borehole. An important positive pressure peak was found to occur as the casing moved with maximum velocity. Important negative peaks were found as the casing was lifted from the slips and as brakes were applied to stop pipe movement. A rigorously formulated theory has successfully predicted the sequence and magnitudes of these positive and negative surges and has established a basis for understanding how they occur.

Both the measurements and theory indicate that the most important pressure surge is usually due to viscous drag of the flowing mud. The theory of viscous-drag pressure surges has been approximated by simplified graphs and calculation procedures to facilitate ready use in field operations. Comparison of measured results with those predicted by the simplified theory shows that the magnitude of this surge can be predicted accurately.

Introduction

It is widely recognized that raising or lowering pipe in a fluid-filled borehole produces momentary variations in fluid pressure, commonly called pressure surges. Both negative (or "swabbing") surges and positive (or "fracturing") surges may occur. In 1934, Cannon measured the negative surges and showed that they could be large enough to cause flow of formation fluids into the wellbore and, in extreme cases, lead to blowout conditions. Later, Goins measured the positive surges associated with lowering pipe. His results and subsequent field operations strikingly demonstrated that pressure surges could be an important factor in some cases of lost returns. In addition, although the evidence is less clear than in the case of blowouts and lost returns, other investigators feel that pressure surges probably play a part in many instances of minor gas cutting, salt-water flow and other hole trouble.

The importance of pressure surges in drilling operations led naturally to attempts to explain the physical causes, nature and magnitude of the surges. Cardwell was the first to publish a theory which allowed the quantitative prediction of momentary pressure variations. He assumed that the drilling fluid was a 300-cp Newtonian fluid in turbulent flow. Most field muds have a considerably lower viscosity and are generally believed to be Bingham plastic in nature a However, Cardwell's results were useful because they were presented in a form convenient for field use and, in some cases, gave a reasonably accurate predicted value for the maximum pressure surge.
Experimental Investigation of Fracturing-Fluid Migration Caused by Spontaneous Imbibition in Fractured Low-Permeability Sands
Authors: Dutta R.. , Lee C.-H.. -H. , Odumabo S.. , Ye P.. , Walker S.C.. C. , Karpyn Z.T.. T. , Ayala H. L.F.. F.
Published: June 2014

During hydraulic-fracturing operations in low-permeability formations, spontaneous imbibition of fracturing fluid into the rock matrix is believed to have a significant impact on the retention of water-based fracturing fluids in the neighborhood of the induced fracture. This may affect the post-fracturing productivity of the well. However, there is lack of direct experimental and visual evidence of the extent of fluid retention, evolution of the resulting imbibing-fluid front, and how they relate to potential productivity hindrance. In this paper, laboratory experiments have been carefully designed to represent the vicinity of a hydraulic fracture. The evolution of fracturing fluid leakoff is monitored as a function of space and time by use of X-ray computed tomography (CT). The X-ray CT imaging technique allows us to map saturations at controlled time intervals to monitor the migration of fracturing fluid into the reservoir formation. It is generally expected for low-permeability formations (5 to 10 md) to show strong capillary forces because of their small characteristic pore radii, but this driving mechanism is in competition with the low permeability and spatial heterogeneities found in low-permeability sands. The relevance of capillarity as a driver of fluid migration and retention in a low-permeability sand sample is interpreted visually and quantified and compared with high-permeability Berea sandstone in our experiments. It is seen that although low-permeability sands are subject to strong capillary forces, the effect can be suppressed by the low permeability of the formation and the heterogeneous nature of the sample. Nevertheless, saturation values attained as a result of spontaneous imbibition are comparable with those obtained for high-permeability samples. Leakoff of fracturing fluids during the shut-in period of a well can result in delayed gas flowback and can hinder gas production. Results from this investigation are expected to provide fundamental insight regarding critical variables affecting the retention and migration of water-based fracturing fluids in the neighborhood of hydraulic fractures, and consequently affecting the post-fracturing productivity of the well.
Lessons Learned From Steam Generation: Novel Chemical Control And Integrity Management During The Commissioning And Start-up Of The Schoonebeek Facilities
Authors: Shepherd Andrew G. , Jonker Edwin , Bayens Peter
Published: June 2014

This paper describes the chemical control and integrity management steps taken during the commissioning and start-up of the Combined Heat and Power plant (CHP) of a large field redevelopment. The chemical controls were carried out using a combination of new and established chemistries in oxygen scavenging, corrosion inhibition and scale inhibition. Carefully designed passivation and slugdosing, in addition to a clear and robust sampling and analysis plan, had a direct impact on the development of these operations. The lessons learned of two boiler systems are discussed together with the improvements implemented to achieve fit for purpose steam generation. This has included for instance, particular attention on the monitoring of boiler feed water quality and use of hydrogen meters. Furthermore magnetite formation was established for two boiler systems. This was confirmed by pH trends in the high pressure drums, sample appearance, hydrogen measurements and analysis of solids taken during various stages of monitoring. The results suggest that magnetite formation occurred at conditions different to what is the established rule of thumb during high pressure start-ups, e.g. 30 bar. It is speculated that such behavior was influenced by the chemical control selected. Key performance indicators (e.g. phosphate operational window) as well as automated chemical dosing is allowing good integrity control of the steam generation system as the facility migrates into steady state operation.
A New Approach for Predicting Inhibited Erosion-Corrosion in CO2-Saturated Oil/Brine Flow Condition
Authors: Hassani Shokrollah , Roberts Kenneth P. , Shirazi Siamack A. , Rybicki Edmund F. , Shadley John R. , Joia C.
Published: June 2014

Chemical inhibition is a common method for controlling erosion-corrosion in offshore mild steel pipelines, tubing and pipe fittings. The paper introduces a new approach for predicting inhibited erosion-corrosion in mild steel pipes including the effects of flow and environmental conditions, sand production, and an oil phase.

When sand is produced, sand particle impinging on piping surfaces can decrease the efficiency of corrosion protection systems such as iron-carbonate scale formation or chemical inhibition and result in severe corrosion and even pitting. The need to be able to predict inhibitor performance under sand production conditions is particularly acute when the wells are deep or off-shore because of the difficulty in running coupon tests to evaluate the inhibitor efficiency at critical points throughout a system. Research reported in this paper is aimed at providing producers with information that will help them make decisions on the design of the well given advanced knowledge of the inhibition options and their predicted effectiveness under sand production conditions. Inhibition mechanisms and the relation between inhibitor concentration and inhibitor coverage are described using adsorption isotherms. The Frumkin isotherm showed the best fit to experimental data for an imidazoline-based inhibitor used in sand-free conditions. Flow loop tests indicated that sand particle erosion decreased the efficiency of the inhibitor. However, Frumkin isotherms modified to handle effects of erosivity, temperature, and oil phase were successfully fitted to erosion-corrosion data. Inhibitor adsorption isotherms, for both sand-free and sand production conditions, were integrated into a mechanistic model for prediction of CO2 corrosion rates as a function of inhibitor concentration and good results were obtained as compared with data.

Results of this study show that the inhibitor adsorption isotherm, modified to handle effects of sand production, temperature, and oil phase can be a valuable tool for predicting inhibited metal loss rates under sand production conditions.
The Significance of Particle Shape in Formation Resistivity Factor-Porosity Relationships
Authors: Atkins E.R. , Smith G.H.
Published: June 2014

Results of laboratory tests are presented to show that the value of "m", in the Archie expression is determined by the shapes of the particles in the system. The value of m, "the shape factor", is constant for a system of particles of a given shape for a range of values. Applying this concept, one can predict relationships for mixtures of particles with different shapes, and these predicted relationships are useful in electric log interpretation.

It is suggested that an equation of the form can be used to describe the properties of natural formations containing varying amounts of sand and clay. From this work and values of "a" and "m" reported in the literature, it appears that in many cases rocks in the same geological horizon have a common primary porosity but contain varying amounts of a particular clay. It is concluded that the equation can be applied to a rock-water system only when values of "a" and "m" have been established for the particular system.

Introduction

The petroleum literature contains many reports of the results obtained by determining formation resistivity factor and porosity of rock samples from oil fields all over the world.
Coral Risk Assessment - Tool Development
Authors: Ulfsnes Amund , Møskeland Thomas , Aarnes Øivin
Published: June 2014

Operators and authorities have a need for an assessment of the impacts from drilling activities on vulnerable fauna communities. There is currently lacking a standardized risk method based on an objective method to perform this type of assessment. A suggestion for a risk based approach for planning of drilling operations with regards to drilling location, location of anchor chains and pennant wires etc. in vulnerable areas (such as coral and sponge areas) is therefore developed. The risk based approach basis are GIS (Geographical Information System) analyses, experiences trough performed monitoring projects, data of prevailing currents, estimates of discharges, potential coral structures and their condition, threshold values with regards to sedimentation (literature) and location of anchor corridors. The risk analysis shall be an input to operator's applications to relevant authorities and will strengthen operator's arguments for planning drilling operations with regards to minimize risk of negative effects on vulnerable habitats such as corals and sponges. It is also as a "stand alone" tool for planning a drilling operation where operators can analyse different alternatives with regards to drilling location and anchor corridors with the lowest risk for vulnerable marine bottom fauna. A risk based approach for assessing the impacts from drilling activities on vulnerable fauna is developed. The risk based method can pin point the risk associated with each structure (for example corals) which may be affected by a drilling operation. By looking at different options for the drilling location and the anchor corridors operators can plan such that the risk for vulnerable fauna (for example corals) are affected by the operation is minimized. The proposed method has enabled operators to minimize risk of vulnerable fauna in the planning phase of a drilling operation.
Monitoring of a Drilling Operation Within a Coral Sensitive area - Case Pumbaa ( Norway)
Authors: Møskeland Thomas , Ulfsnes Amund , Sverdrup Line , Moe Jannecke A. , Løkken Morten
Published: June 2014

Deepwater corals (Lophelia) were identified in the vicinity of the location of the exploration well Pumbaa (NOCS 6407/12-2) on the Norwegian Continental Shelf where a drilling operation was carried out by the GDF SUEZ E&P Norge AS (GDF SUEZ). Det Norske Veritas AS has on behalf of GDF SUEZ conducted an environmental monitoring of drilling activities at Pumbaa (NOCS 6407/12-2).

Because of registrations of deep water corals (Lophelia) in the Pumbaa area, and due to specific requirements - a relatively comprehensive monitoring of the drilling activities was carried out. Only the drill cuttings from the top hole sections were discharged at the sea floorThe generated cuttings and used mud from deeper well sections were not discharged to sea. In order to increase the distance to the nearest corals from the discharge point, a Cuttings Transport System (CTS) was used to transport discharges from the top hole sections and all discharges were at 300m distance NNW (310 degrees) of well location. The main objective of the monitoring was to assess effects from the drilling activities on the corals south (and nearest) of the drilling location. The monitoring program included measurements of current, turbidity and sedimentation, as well as sampling of sediments from the seafloor. Sediment samples from the seafloor and sedimentation traps were analyzed for heavy metals and physical parameters. Coral structures were visually inspected before, during and after drilling operations.
Propping Fractures with Aluminum Particles
Authors: Kern L.R. , Perkins T.K. , Wyant R.E.
Published: June 2014

This paper presents information on the use of a new propping agent (malleable aluminum particles) which has been used successfully for producing high-conductivity fractures.

The conductivity of a packed fracture depends oil the width of the fracture as well as the permeability of the propping material. It is significant that the flow capacity of a propped crack is often increased many fold by propping the crack with a sparse distribution of particles. However, the flow capacity of a sparsely propped crack can be limited by two phenomena:crushing of the propping particles, andembedment of the propping particles in the formation walls.

Malleable aluminum particles exhibit interesting properties which tend to overcome these limitations. As high loads are applied to the particles they will deform slightly, rather than shattering. The deformation results in a greater bearing area against the formation wall. This reduces the stress on the particle and reduces particle penetration into the formation.

The behavior of aluminum particles under load and the bearing capacities of several formation rocks have been measured in the laboratory. By properly using these data, as explained in this paper, the flow capacities of aluminum-propped cracks can be calculated for a variety of conditions.

Aluminum particles have been used successfully in the field to prop fractures. Where high-conductivity fractures were needed, the aluminum-propped fractures have given greater well stimulation than could have been expected for conventional fracturing processes.

Introduction

The purpose of a hydraulic fracture treatment is to create a conductive channel from the wellbore out into the oil or gas formation. The word conductive is emphasized because we believe that the fracture conductivity (flow capacity) is one of the most important factors influencing fracturing results.

Previous papers have pointed out the additional well stimulation that can sometimes be achieved by increasing fracture conductivity. Several years ago, we investigated in some detail the effect of fracture conductivity on productivity increases to be expected from vertical fractures. Both electrical analog and theoretical studies of unsteady-state flow behavior were made. A discussion of the electrical analog equipment and some of the results of the study were given in a previous paper by Dyes, Kemp and Caudle. Further details were given recently by McGuire and Sikora.
Phase Behaviour of C3H8/n-C4H10/Heavy-Oil Systems at High Pressures and Elevated Temperatures
Authors: Li Huazhou , Yang Daoyong (Tony)
Published: June 2014

Phase behaviour of C3H8/n-C4H10/heavy-oil systems at high pressures and elevated temperatures has been experimentally and theoretically investigated. Experimentally, a versatile pressure/volume/temperature (PVT) system is used to determine the liquid/vapour phase boundary (i.e., saturation-pressure lines) and swelling factors of C3H8/n-C4H10/heavy-oil systems with varying compositions at high pressures up to 5030.0 kPa and elevated temperatures up to 396.15 K. During the experiments, heavy oil is added continuously into the solvent and the injection process can be terminated within a short period. No noticeable asphaltene precipitation has been observed throughout the measurements for the four mixtures. The viscosities of the corresponding solvent(s)-saturated heavy-oil systems are measured by using a customized capillary viscometer at 298.85 K. Theoretically, the volume-translated Peng-Robinson equation of state (PR EOS) (Peng and Robinson 1976) with a modified alpha function is used to model the experimental phase behaviour of C3H8/n-C4H10/heavy-oil systems. Two binary-interaction-parameter (BIP) correlations, respectively developed for the C3H8/heavy-oil system and n-C4H10/heavy-oil system, are incorporated into the volume-translated PR EOS model. The two BIP correlations together with the volume-translated PR EOS are found to be capable of predicting the saturation pressures and swelling factors of the C3H8/n-C4H10/heavy-oil systems with a good accuracy, although the prediction accuracy is reduced at temperatures close to the critical temperature of a pure solvent. In addition, comparison of five commonly used mixing rules indicates that the Lobe's mixing rule (Lobe 1973) is more appropriate to predict the viscosity of heavy oil diluted by C3H8 and/or n-C4H10.
Effect of Temperature on VAPEX Performance
Authors: Haghighat Parnian , Maini Brij B.
Published: June 2014

Incorporating some heat injection along with solvent injection appears to bethe most viable option for improving the oil-drainage rate of vapour-assistedpetroleum extraction (VAPEX) in extraheavy-oil formations. This study wasintended to quantify the maximum possible increase in VAPEX drainage rate thatcan be obtained by heating the formation to a target temperature. Theexperimental phase of this study involved conducting VAPEX experiments in alarge high-pressure physical model, packed with 250-darcy sand, using propaneas the solvent. The physical model was preheated to 40, 50 and 60°C, andpropane was injected at the same test temperature but different injectionpressures to observe how injection pressure affects oil-drainage rate atelevated temperatures. In the experiments at elevated temperatures, but withoutincreasing the injection pressure, higher rate of oil production was achievedin the early stages of the process. However, a stabilized rate of oilproduction did not show pronounced improvement caused by a lower solubility ofpropane in the oil at higher temperatures. Increasing injection pressure alongwith increasing the test temperatures was successful in accelerating the oilproduction. The oil used in these experiments was found to become mobile withthe increase in temperature even without solvent dissolution. As a result, thetotal rate of oil production appeared to be controlled by two mechanisms: (1)by solvent dissolution and oil mobilization at the boundaries of the vapourchamber and (2) by pure free-fall gravity drainage beyond the vapour chamberwherever gravity head was sufficient to push the mobile oil toward theproduction well. The results of this these tests define the upper limit of oilrates achievable with heated solvent injection. They can also be used to assessthe applicability of VAPEX to warm reservoirs naturally (e.g., in Venezuela)and reservoirs with mobile oil in place.
New Software for Processing of LWD Extradeep Resistivity and Azimuthal Resistivity Data
Authors: Sviridov M.. , Mosin A.. , Antonov Yu.. , Nikitenko M.. , Martakov S.. , Rabinovich M.B.. B.
Published: June 2014

In petroleum exploration, reservoir navigation is used for reaching a productive reservoir and placing the borehole optimally inside the reservoir to maximize production. For proper well placement, it is necessary to calculate in real-time the parameters of the formation we are drilling in and the parameters of formations we are approaching. On the basis of these results, a decision to change the direction of drilling could be made. Modern logging-while-drilling (LWD) extra-deep and azimuthal resistivity tools acquire multicomponent, multispacing, and multifrequency data that provide sufficient information for resolving the surrounding formation parameters. These tools are generally used for reservoir navigation and real-time formation evaluation. However, real-time interpretation software is very often based on simplified resistivity models that can be inadequate and lead to incorrect geosteering decisions.

The core of the newly developed software is an inversion algorithm based on transversely isotropic layered Earth with an arbitrary number of layers. The following model parameters are determined in real time: horizontal and vertical resistivities and thickness of each layer, formation dip, and azimuth. The inversion algorithm is based on the method of the most-probable parameter combination. The algorithm has good performance and excellent convergence because of its enhanced capability of avoiding local minima. This capability enables interpretation of real-time resistivity data, including azimuthal and extra-deep measurements.

A graphical user interface (GUI) was developed to provide an interactive environment for each stage of the resistivity data interpretation process: preview of input resistivity logs, initial preprocessing and filtering of raw data, creation of initial guess, running inversion and viewing inversion results, and quality-control indicators. Applications of the developed software will be shown on a series of synthetic examples and field data from the North Sea and Gulf of Mexico (GOM). This newly developed software is currently in use for real-time reservoir navigation and post-well analysis.
Optimised Solids Control in Arctic Environments
Authors: Dahl Bjørn , Omland Tor Henry , Saasen Arild
Published: June 2014

A significant cost issue is related to solids control ant the affiliated waste production during drilling. This cost issue includes the reduced drilling efficiency due to poor solids control when the drilling fluid temperature is low. The primary solids control device is the shale shakers. The preferred shakers have two or three decks that all separate particles from the drilling fluid. Especially when the temperature is low, the flow through the screens on these shakers is limited leading to a large discharge of drilling fluid along with the drilled cuttings.

To increase the efficiency of the shakers a new header box is developed that change the direction of the drilling fluid entering the shakers top deck. On several North Sea operations this device has successfully been used to divert the flow onto the entire top deck screen. This made it possible to run the equipment with finer screens than usual; leading to operating with cleaner drilling fluids than usual and thereby faster drilling rate at the same time as the occupational hygiene in the shaker room was significantly improved. The paper describes in detail how the shakers were modified with the header box and how the shakers were run to optimise drilling performance even when the drilling fluid was cold.
The Estimation of Filtration Reservoir Properties with Log Data
Authors: Kozhevnikov D. A. , Kovalenko K. V. , Deshenenkov I. S. , Petrov A. N.
Published: June 2014

This paper is devoted to the development of capillary pressure and relative/phase permeabilities petrophysical models for different lithotypes of granular reservoirs. Proposed models describe core analysis data better than widely used models (Brooks-Corey model, J-function, Tiksie model, Burdine model). Models are verified on the representative core samples collections (over 200 samples) – sandstones with complex mineral composition from different fields worldwide (Western & Eastern Siberia, Caspian region, Middle East, Alaska). For described formations effective porosity is single value reservoir indicator. Control parameters of developed models have strong correlations with reservoir properties.

Effective and dynamic porosities, hydrocarbon saturation in effective pore space (effective hydrocarbon saturation) determined with well logging data provide evaluation of relative/phase permeability values and hydrocarbon distribution in transition zones.

The adaptive well logging data interpretation technology is applied for effective porosity and saturation determination. This technology is based on the effective porosity petrophysical model of granular reservoirs. It provides prediction of effective porosity values in reservoir conditions with standard well log data interpretation (spontaneous potential log, formation density log, gamma-ray log, neutron log and sonic log). The adaptive technique of resistivity log data interpretation is established for determination of effective hydrocarbon saturation. Proposed models of capillary pressure and relative/phase permeabilities are used in dynamic reservoir properties prediction algorithms with well logging data. Dynamic properties are transferred in digital geological and hydrodynamic models for reservoir development process simulation.

Fluid filtration and mass transfer processes are the basis of the oilfields development for reservoirs with complex structure. Obtained results are applied for fluid filtration processes modeling and reservoir development technology design.
Investigation of Abrasive-Laden-Fluid Method For Perforation and Fracture Initiation
Authors: Pittman Forrest C. , Harriman Don W. , St. John James C.
Published: June 2014

This paper mentions briefly the history of hydraulic jetting as applied to perforating and fracture initiation. It points out the advantages of hydraulic perforation and undercutting as an aid for creating a fracture at the point desired rather than depending upon the weakest point in the formation for breakdown.

It describes early experimental work with jet nozzles in search of better nozzle materials. The effect of splash-back damage and its subsequent influence on jet body and tool design during this work is discussed.

A series of cutting-rate curves for jets cutting steel and steel-cement-formation combinations is presented to show the effect of hydrostatic head and the point of diminishing returns with respect to cutting time.

There is a series of photographs showing various types of rock formation in which perforation and undercutting tests were made. These stones were drilled and the casing cemented in place as in an actual well. The casing was perforated and circularly cut as if preparing for a fracturing job.

The conclusion reached in the paper is that hydraulic jetting with sand-laden fluid can be used for perforating and undercutting casing, cement and formation rock for the intended purpose of inducing the formation to fracture at a desired point.

INTRODUCTION

Hydraulic jetting as a means of cleaning a formation during acidizing has been used for many years. The acid-jet gun was used to clean formation and for drilling cement from casing with acid. This tool was dropped to a seating ring installed on the tubing and could be retrieved by reverse circulation or wire line. In this process, the fluids were directed against the formation to clean and penetrate beyond the mud-damaged area. After the development of the hydraulic fracturing process, interest in jetting the formation with abrasive-laden fluid was renewed. The cutting action of abrasive fluid on pumping equipment, which is a well known problem, has been utilized to perforate and undercut casing, tubing and formation. In this process, surface areas are provided in the formation on which the fracturing pressures may work to produce a fracture at the location desired.
An Electrodeless System for Measuring Electric Logging Parameters on Cores and Mud Samples
Authors: Fatt Irving
Published: June 2014

Introduction

A recently developed system for measuring electrical resistivity of liquids without use of electrodes offers some interesting possibilities in electric logging technology. The equipment as supplied by the manufacturer is satisfactory for continuous mud logging on a drilling rig or for measuring mud or filtrate resistivity in the laboratory. A simple modification of the commercially available instrument makes it suitable for measuring resistivity of core samples in the laboratory.

The continuous measurement of mud resistivity on a drilling rig is a convenient means for detecting mixing of formation water with the drilling mud. Such information is useful to the geologist, the mud engineer and the logging engineer. However, continuous mud resistivity logging by conventional electrode-type resistivity cells is beset with difficulties. The mud, sand and rock chips abrade the electrodes, thereby changing the cell constant and eventually destroying the cell. Also, additives and crude oil in the mud may poison the electrodes by coating them with a nonconductive material. An electrode-type resistivity cell, therefore, may give erroneous readings under certain conditions. Electric logging companies circumvent the electrode poisoning problem by using a four-electrode resistivity cell for measurement of mud resistivity. In this cell, change in electrode area does not change the cell constant. However, the four-electrode cell is difficult to adapt for continuous reading and does not solve completely the problem of electrode abrasion by the sand and cuttings in the mud.

The measurement of electric logging parameters on core samples in the laboratory encounters some of the same problems discussed in connection with mud logging. Ideally, the electrical resistivity of a core sample should be measured by placing platinum black electrodes in direct contact with the plane ends of a cylindrical or rectangular sample. Platinum black electrodes however, are much too fragile and easily abraded to be brought in contact with a rock sample. Also, oil or other constituents in the fluid contained in the sample will poison platinum black. In practice, gold-plated brass electrodes, in an AC bridge circuit operating at about 1,000 cps, are used for routine core analysis. For more precise work in research studies, a four-electrode scheme is used. Preparation of the samples for the four-electrode method is much too involved for routine core analysis.
Jumps in Proved Unconventional Gas Reserves Present Challenges to Reserves Auditing
Authors: Weijermars Ruud
Published: June 2014

This study analyzes the typical challenges and opportunities related to unconventional-gas-reserves maturation and asset performance. Volatility in natural-gas prices may lead to downgrading of formerly proved reserves when the marginal cost of production cannot be sustained by the wellhead prices realized. New US Security and Exchange Commission (SEC) rules have accelerated the growth of unconventional-gas reserves, which in a way is an additional but unintended source of volatility and hence risk. Concerns about security of investments in unconventional-gas assets are fuelled by the effects of volatile natural-gas prices on production economics and by uncertainty about stability of reported reserves. This concern is exacerbated by an unprecedented rise in proved undeveloped gas reserves (PUDs) reported by unconventional-gas operators, arguably effectuated by favorable interpretations of PUDs when applying the new SEC accounting rules. This study includes a benchmark of proved reserves reported by two peer groups, each comprising four representative companies. The peer group of conventional companies includes Exxon, Chevron, Shell, and BP, and the unconventional peer group is made up of Chesapeake, Petrohawk, Devon, and EOG. Possible sources of undue uncertainty in reported reserves are highlighted, and recommendations are given to improve the reliability of reported reserves, especially from unconventional field assets.
Atomic-Force Microscopy: A New Tool for Gas-Shale Characterization
Authors: Javadpour Farzam , Moravvej Farshi Mohammad , Amrein Matthias
Published: June 2014

An atomic-force microscope (AFM), a relatively new tool for studying surface characterization, can generate image features down to atomic resolution. Not only can the AFM obtain topographic images of surfaces, but it also can simultaneously identify different materials on a surface at high resolution. Since its invention in the 1980s, AFM has been used in material science and medical research, although it has not received the attention that it probably deserves in reservoir engineering. The emergence of unconventional shale-gas reservoirs, however, has opened new research frontiers for the AFM in the field of reservoir engineering. The unique capabilities of the AFM make it ideal for studying nanopores, organic materials (kerogen), minerals, and diagenetic fractures in shales. It also can be used to measure localized bulk modulus of elasticity on a surface for further implications in geophysical exploration and designing hydraulic fracturing. We introduce different AFM techniques for all these applications, along with example results.
Successful Cementing Through Bottomhole Drilling Assemblies
Authors: Godøy Rune , Grude Sølve , Dyrkorn Cecilie , Illuminati Roberta , Rørvik Ola
Published: June 2014

This paper summarizes 10 years of experiences on pumping cement through bottomhole drilling assemblies - BHAs. Despite a lot of industrial skepticism, a total of 79 cement jobs have been performed through a variety of drilling assemblies, in 3 categories of job types:

Curing critical mud losses to restore well control Plugging back pilot holes Planned plug or squeeze jobs

The job objectives were met for all the cement jobs performed, and high risk well control situations were resolved. The cementing operations have been performed from different types of offshore installations, like fixed platforms, semi-submersible rigs, as well as from TLP's - Tension Leg Platforms.

Most significantly, critical mud losses have been cured by pumping totally 13 cement jobs through rotary steerable drilling assemblies. Losses were cured and well control restored by performing jobs mainly through 8 ½ - and 12 ¼" drilling assemblies. The most severe case handled HPHT conditions and cesium formate drilling fluid.

By taking a controlled risk, the total well risk is significantly reduced. Time and huge costs are saved by performing cement jobs that are instinctively considered as a threat to well control. By planning these cement jobs carefully, the total risk of performing the operation through the bottom hole assembly is reduced.

After gaining experience from some severe, un-planned lost circulation incidents, a best practice was developed and implemented in order to be better prepared, especially for the un-planned events. The same procedures have also been implemented in the planning phase of drilling operations and some cementing operations are planned and executed this way.
Variations in Bounding and Scanning Relative Permeability Curves With Different Carbonate Rock Types
Authors: Dernaika M.R.. R. , Basioni M.A.. A. , Dawoud A.. , Kalam M.Z.. Z. , Skjæveland S.M.. M.
Published: June 2014

Relative permeability curves generally exhibit hysteresis between different saturation cycles. This hysteresis is mainly caused by wettability changes and fluid trapping. Different rock types may experience different hysteresis trends because of variations in pore geometry. Relative permeability curves may also be a function of the saturation height in the reservoir.

A detailed laboratory study was performed to investigate relative permeability behavior for a major carbonate hydrocarbon reservoir in the Middle East. Representative core samples covering five reservoir rock types (RRTs) were identified on the basis of whole core and plug X-ray computed tomography (CT), nuclear magnetic resonance (NMR) T2, mercury injection capillary pressure (MICP), porosity, permeability, and thin-section analyses. Primary-drainage (PD) and imbibition water/oil relative permeability (bounding) curves were measured on all the five rock types by the steady-state (SS) technique by use of live fluids at full reservoir conditions with in-situ saturation monitoring (ISSM). Imbibition relative permeability experiments were also conducted on the main RRT samples to assess the relative permeability (scanning) curves in the transition zone (TZ) by varying connate-water saturations.

Hysteresis effects were observed between PD and imbibition cycles, and appeared to be influenced by the sample rock type involved (i.e., wettability and pore geometry). Variations in relative permeability within similar and different rock types were described and understood from local heterogeneities present in each individual sample. This was possible from dual-energy (DE) CT scanning and high-resolution imaging. Different imbibition trends from both oil and water phases were detected from the scanning curves that were explained by different pore-level fluid-flow scenarios. Relative permeability scanning curves to both oil and water phases increased with higher connate-water saturation. Relative permeability to oil was explained on the basis of the occupancy of the oil phase at varying connate-water saturations. The change in the water relative permeability trend was addressed on the basis of the connectivity of water at the varying connate-water saturations. These results and interpretations introduced an improved understanding of the hysteresis phenomena and fluid-flow behavior in the TZ of a Cretaceous carbonate reservoir that can assist in the overall reservoir modeling and well planning.
What the Mating Behavior of Birds Can Teach Us About Corporate Decision Making
Authors: Lehman John
Published: June 2014

The combination of computer technology and decision theory has failed to produce the dramatic improvement in the quality of corporate decisions that some predicted. In this paper, I suggest that this failure comes, at least in part, because too little attention has been paid to the environment in which corporate decisions are made. Specifically, this article proposes that corporate decision processes are not constructivist rationality, but more closely resemble the ecological rationality of biological systems shaped by evolution and natural selection. That is, decision processes in corporations evolve over time to satisfy, although not necessarily to optimize, both stated and unstated objectives subject to complex information cost structures and constraints. To illustrate, examples of persistent information asymmetry and economic signaling in nature and in decision processes are shown. Finally, this article suggests that improved understanding of the forces that impact the evolution of corporate decision processes may allow decision theory to come closer to achieving its potential.
Analysis of Transient Linear Flow in Stress-Sensitive Formations
Authors: Qanbari F.. , Clarkson C.R.. R.
Published: June 2014

Rate- and pressure-transient analysis of unconventional gas and oil reservoirs is a challenge because of the complex reservoir characteristics that dictate flow. Transient linear flow is usually an important flow regime for these reservoirs and is often associated with linear flow to induced hydraulic fractures. One of the complications in the analysis of this flow regime is stress sensitivity of porosity and permeability. This work provides a new method for analysis of transient linear flow in stress-sensitive tight oil reservoirs.

A correction factor is used to correct the results of the conventional method for analysis of transient linear flow in tight oil reservoirs. A new method is developed for calculating the correction factor by use of an analytical solution to the flow equation. The correction factor is used for production-data analysis of two examples for constant-pressure and constant-rate production. The results indicate that the correction factor becomes more important for higher values of permeability modulus and pressure drawdown. Further, we demonstrate that the correction factor can eliminate the considerable error of the conventional analysis method in estimating initial reservoir permeability or hydraulic fracture half-length.