bluuebunny/crossref_metadata_2025 huggingface dataset:
Immigration enhances fast growth of a newly established source population
Authors: Santoro Simone , Green Andy J. , Figuerola Jordi
Published: November 2015

Immigration and local recruitment play a central role in determining the growth rate of breeding populations. Unraveling these processes in newly established populations is of great importance to increase our understanding of how species change their distributions in response to global change. We studied the largest colony of glossy ibis (Plegadis falcinellus) in Western Europe (established in 1996 in Doñana, SW‐Spain) by using capture‐recapture methods, count estimates, and projection matrix modeling to: (1) test the effect of resource availability and competition on local recruitment dynamics, (2) investigate the contribution of local recruitment vs. immigration on population growth, and (3) assess the role of this population in source/sink dynamics. We found different dynamics before and after the establishment of satellite colonies in Doñana in 2004. Between 1996 and 2003, the population increased rapidly, fueled by immigrants (≈58 breeding females/yr). Between 2003 and 2007, however, both colony size increase and immigration were negligible. Immigration played a major role in colony growth, but simultaneously this colony was a source population driving expansion of the species range as suggested by (1) absolute and relative estimates of the observed growth rate relative to that predicted by self‐recruitment, and (2) numerous observations of Doñana‐born individuals breeding elsewhere. Local recruitment, which was particularly high for first‐year individuals (probability >0.8 for the early study years), was not directly related to resource availability or previous‐year breeding success. Local recruitment decreased rapidly at a threshold population size, however, when other satellite colonies became established at Doñana. Our study suggests that even when recruitment at an early age and high productivity are observed, immigration can still play a pivotal role in promoting the fast growth of new populations at the edge of a species range, at least until density‐dependent effects arise. This process can be so fast that within a few years a new population can itself become a source population, further driving range expansion of the species.
Make in India: How the campaign stimulated industry led investment in the country and what are the key issues which need to be addressed
Authors: Patel Keshav
Published: November 2015

The flagship campaign led by NDA government at the union level has brought many changed perceptions and made the industry and investors across world to consider investing in India. The red carpet for the industry has helped bringing investments into the Indian industrial activities. This work focuses on the campaign as to its relevance and favor to the investors who invested/ want to invest into Indian business sector. This paper tries to evaluate the campaign in the general terms.
Remedial theology: An exploration into the factors-Religious conviction, mysticism and wellbeing.
Authors: Kaur Tarundeep
Published: November 2015

Spirituality and religion have been seen as beneficial, harmful, and irrelevant to health. An effort was made to examine the recent research on this topic. The focus was on: defining spirituality and religion both conceptually and operationally. The rapidly accumulating evidence on spirituality further confirmed that personal spirituality has important influences on healthcare outcomes however it is difficult to integrate into daily medical practice. However medical spirituality was studied as a distinct interdisciplinary with its own well-developed body of clinical evidence, clinical skill and with well-defined clinical boundaries. An effort was made to integrate the new knowledge, and help anticipate developing "turf issues."
Experiment Investigation of Steam Flooding of Horizontal Wells for Thin and Heterogeneous Heavy Oil Reservoira
Authors: Huang Shijun , Huang Chenghui , Cheng Linsong , Liu Tian , Chen Zhiming , Mao Wenhui
Published: November 2015

Steam flooding of horizontal wells has long been considered as one of the most effective methods to unlock thin heavy oil reservoirs. Large volumes of heavy oil are located in heterogeneous porous medium containing high permeability wormholes or low permeability shale barriers. Strong heterogeneity can be the main result of early steam channeling. There is a question of how the heterogeneities enhance or hinder the steam chamber advancement, the flow of high viscous oil, steam and condensed water under a steam flooding process in a thin heavy oil reservoir. The shape of the steam chamber is a key element of calculating steam sweep efficiency, confirming the recoverable reserves, determining the moment of steam channeling, optimizing the well spacing, etc. In this paper, we present a series of physical experiments investigating the steam flooding using horizontal wells for thin and heterogeneous heavy oil reservoir. The apparatus mainly consists of simulated formation containing dual parallel horizontal wells. The shape of the steam chamber is obtained by using the Kriging interpolation method. The steam chamber sweep efficiency, oil recovery and water cut of homogeneous model and heterogeneous models are compared. The results indicate that the low permeability zones greatly hinder the development of steam chamber, resulting in poorer sweep efficiency, earlier steam breakthrough, more residual oil, as well as lower oil recovery, higher water cut, less liquids and oil production. The pressure behavior of the horizontal wells are also investigated.
Hydrocarbon Recovery Maximization in Reservoirs Located Close to Potential Water Producer Horizons: New Proposed Methodology to Combine Water Control and Fracture Stimulation Processes
Authors: Sierra Leopoldo , Eoff Larry
Published: November 2015

Hydrocarbon production and recovery maximization can be a challenging task in some specific areas or reservoirs. Specifically, in low permeability environments, hydraulic fracturing is a necessary step to improve the wells productivity and it can be easily justified or applied in reservoirs where a nearby water bearing zone is not present or the water bearing zone is far away from the productive horizons.

When bottom water or water bearing zones are located near the oil producer layers, hydraulic fracture stimulation is normally aborted or the potential layer is abandoned or not completed; unfortunately, the luxury of stimulation or completion abortion is not really the best decision because a large amount of hydrocarbons is located in such complex environments.

For the situations where the fracture stimulation could not be avoided, the industry has used different alternatives to minimize water production. These include selective perforation and controlled fracture stimulation, selective water control treatment into the water producer layer followed by fracturing, or combining the water control and fracture stimulation in one. For the latter methodology, the water control chemical is squeezed first into the fractured interval or the chemical is added into the fracturing fluid pad to minimize water mobility. However, this methodology relies on the compatibility of the fracturing fluid and the water control chemicals or the migration of the water control chemical from the fracturing fluid system to the water source layers to be effective.

This paper proposes a new methodology to minimize water intrusion in cases where fracture stimulation is necessary in areas with bottom water or water bearing zones near the oil producer layers by performing on-the-fly coating of proppant with a relative permeability modifier (RPM) chemical. In the new proposed methodology, water mobility in the water producer layer will be controlled by the proppant bed coated by the RPM.
Successful Execution of an Exploratory Drilling Program Within Extremely Sensitive Environments in Ecuador
Authors: Benalcazar F. L. , Valdivieso S.
Published: November 2015

In Ecuador, back in 2006-2007, the Operator of Blocks 14 and 17 concluded a large exploration project with the construction of Batata 2 well pad and the drilling of two exploratory wells pursuing the confirmation and development of oil reserves identified during the seismic work started in 2003 by EnCanEcuador (Subsidiary of EnCana), in the north area of Block 14. All this development occurred within the Yasuni National Park, one of the natural areas with the highest biodiversity in South America and also traditional land of peoples living in voluntary isolation (Tagaeri and Taromenani).

The Company developed and implemented implementation a sound environmental and social project management that included a sensitive stakeholders engagement and involving plan, the implementation of a permanate HSE team on site focused on audit operations on a daily basis, a community monitoring program, an strong constractor selection process, and a set of best construction and drilling parctoces.

This paper summarizes some of the most important elements of project planning and execution of Batata 2 well pad. Now, years after its execution, we can do a retrospective analysis to identify some of those practices, to highlight them and to present them to our colleagues in the industry. Now the Life Cycle Management is a well know environmental management tool, and the Batata 2 project is a suceesful study case of a properly managed project that represents the commitment from the oil industry to develop and execute projects under the highest social and environmental standards.
A Comprehensive Workflow for Reservoir Characterization and History Matching Applicable to Cretaceous Naturally Fractured Reservoirs in Mexico
Authors: Mehranfar R. , Larez C. J. , Paredes J. E. , Villasana J. C.
Published: November 2015

Most of the Cretaceous fractured reservoirs in Mexico are producing from reservoirs with very poor matrix quality and therefore matrix, for the most part, cannot support the fluid flow into fracture and further on towards the wellbore. Considering other important factors like reservoir rock wettability, which is supposed to be oil wet for this type of rock, small matrix block height, and possible capillary continuity between blocks, the effective production mechanism from these reservoirs (fluid transfer from matrix to fracture) changes from capillary imbibition dominated to gravity drainage and viscos dominated.

Based on the interpretation of field production data as well as discrete fracture network modeling results, most of the movable oil is considered to be stored in the fractured system, and little participation from matrix to the produced fluid is expected. Also considering the very heterogeneous nature of these reservoirs caused by extended systems of faults and fractured, it is very common that this kind of reservoirs can be divided into different compartments with completely different dynamic behavior.

In this work, we try to present a dynamic workflow to compartmentalize the reservoir into isolated or partially isolated blocks, which is the first step in reservoir history-matching process. Later, and through considering the reservoir effective production mechanisms that are discussed in the bulk of the study, a layered history matching process will be presented. In developing this workflow, the raw and interpreted data as well as the final reservoir history-matched models of several fields located in the area have been taken into account to be able to calibrate the workflow and propose a comprehensive procedure that can be of use in similar cases.
Fracturing-to-Production Simulation Approach for Completion Optimization in the Vaca Muerta Shale
Authors: Suarez M. , Pichon S. , Lacentre P. , Badessich M. Fernandez
Published: November 2015

Production modeling is a process that requires analyzing several steps, from reservoir characterization, completion and hydraulic fracturing, up to the optimization in the production system. Traditionally these processes can be analyzed independently with separated specialized tools. However in unconventional reservoirs, as the Vaca Muerta shale, dependency between the stimulation treatment and the well productivity is critical. This work proposes a workflow to evaluate the joint impact of hydraulic fractures with the static and dynamic characterization of the reservoir.

The available static information (geophysics, petrophysics, geomechanics and natural fracture interpretation) is integrated to build a geological model. Then, hydraulic fracturing is simulated numerically using the Unconventional Fracture Model (UFM). The model takes into account the interaction between the existing natural fractures and the created hydraulic fractures during the stimulation treatment. The resulting geometry of the hydraulic fractures is gridded in an unstructured manner. The model reproduces explicitly the volume and permeability with the appropriate distribution along each branch of hydraulic fractures according to the executed completion. Dynamic simulation can be run to perform a history match of the available production data. Hydraulic fracture geometry, driven by geomechanics and natural fractures, is a key component of the process and might be reviewed if no production match can be achieved making the overall workflow iterative. Additionally, automation through assisted history matching is proposed to investigate different possible solution and reduce the timeframe of the study.

Once calibrated with production, the model allows several applications. The different possible solutions considered by the assisted history match process permit the evaluation of the uncertainty of final recovery when forecasting production. Sensitivity analysis over a given hydraulic fracture geometry shows the major role of the matrix saturation and conductivity degradation over the final recovery. Completion can be optimized by considering different scenarios and showing the direct correlation between generated propped surface and well productivity. Different fracture designs can be investigated to increase the propped surface highlighting the importance, not only of the proppant volume, but also of the proppant transport capability of the fracturing fluids to be used.
Geomodeling Workflow Adapted to a Mature Extra Heavy Oilfield. Case Study: Modelization of Petrocedeño Deltaic Reservoir for the EOR Polymer Project
Authors: Mulder R. , Tinedo C.
Published: November 2015

The following paper describes the geomodeling workflow developed for the deltaic reservoirs setting of the Petrocedeño onshore extra-heavy oil field. A modelling strategy was defined to meet the requirements of history matching and polymer injection simulation by first identifying, then implementing in the model, the key geological features which influence production and polymer injection. Furthermore, the methology defined allows the model to respect a vast amount of well data, and to be easily updatable. As a case study, a sector model was constructed in the area selected for the polymer injection pilot project.

In the first step the geological concept is incorporated using deterministic paleogeographic maps, defined using well data and net-sand maps to delineate the main channel belts and floodplain depositional environments. Within this framework, facies associations are modeled using a stochastic algorithm (SIS), with as an additional input a probability cube guiding their vertical and lateral distributions. The probability cube combines the vertical proportion from well data with probability maps derived from shale thickness maps between reservoir units. Facies are consequently modeled (SIS) within the facies associations, followed by classical petrophysical modeling (SGS) per facies.

This workflow's novelty is in the two step modeling of facies associations within the depositional environments prior to facies and petrophysical modeling. The first step gives a strong deterministic input, adapted to a mature field constrained with over 1000 wells. The second step, stochastic modeling within a deterministic framework, has several advantages.

A key aspect is the easy incorporation of all well data, including horizontal wells, as well as the ability to quickly update the model with automatic workflow. With 70 new wells being drilled each year this is a significant advantage. Furthermore, the use of a custom made probability cube permits an accurate representation of the vertical trends within each interval as well as the distribution of barriers between reservoir units. Finally, stochastic approach allows better control of the distribution of the channels internal heterogeneities, a key factor for flow simulation in a polymer injection project.
Oil Recovery in Low Permeability Sandstone Reservoirs Using Surfactant-Polymer Flooding
Authors: Marliere C. , Wartenberg N. , Fleury M. , Tabary R. , Dalmazzone C. , Delamaide E.
Published: November 2015

Surfactant-Polymer flooding is usually not applied in low permeability reservoirs mainly due to injectivity problems in the presence of mobility control agents. Indeed, in the case of surfactant-polymer injection in low permeability formation, one of the major problem is to avoid the plugging of the core due to the jamming of polymer molecules in small pores. Hence, a compromise between molecular weight, concentration and viscosity must be determined. Here we demonstrate the feasibility of a surfactant-polymer EOR process in a sandstone reservoir core with a permeability around 1 mD.

Coreflood experiments were carried out on a sandstone reservoir core using a formulation consisting of a low molecular weight HPAM polymer and a typical oil recovery surfactant, that improved i) the mobility control as well as ii) the interfacial tension decrease between oil and the aqueous phase. The studied system consisted in a 1 to 3mD permeability and 15% porosity sandstone reservoir core, with dodecane as model oil and a 64g/L NaCl brine at 60°C. Specific petrophysical protocols were used to avoid non-uniform saturation profiles at irreducible water saturation (Swi) generated by strong capillary effects that are typical of low permeability media. In addition to the usual mass and volume measurements, we also used the X-Ray CTscan imaging in order to obtain saturation profiles at various steps of the EOR process.

The injection of a low molecular weight polymer solution was possible without plugging the core by choosing the polymer concentration so as to increase the mobility ratio but remaining under the critical entanglement concentration. A first slug of surfactant-polymer solution was injected followed by a polymer postflush. Due to the high amount of clays in the low permeability rocks we used a salinity gradient in postflush to minimize the important adsorption of the surfactant during the injection of the formulation and increase the oil recovery of the process. Saturation measurements were done after each experimental step (100% brine, Swi, ROS and Sor) and revealed a good correlation between the different methods. Thanks to this strategy it was possible to decrease the residual oil saturation (Sor) by at least a factor 2, increasing oil recovery in the range of 40–60% ROIP, compared to standard waterflooding.

The novelty of this work is to use the combination of surfactant and polymer in very low permeability sandstone rocks.
Tena Sandstone: A New Productive Reservoir in the Oriente Basin
Authors: Ruiz R. , Bustos J.
Published: November 2015

The Tena Sandstone, a small horizon belonging to the Tena formation, is presented regionally in the Oriente basin, but has high variability in its productive characteristics, to the point that oil reserves have been recovered from this horizon only in the Blanca-1 well. The information available from the Putumayo, Oriente, and Marañon basins in the upper Cretaceous to Paleogene periods was revised, and a summary table of correlation was performed. Based on the information from the Blanca-1well, and other nearby wells, the stratigraphic features of the Tena Sandstone have been defined. Using 3D seismic data and petrophysical information obtained from wells drilled in the area, the structural and the static models have been elaborated. Considering the production history and the behavior of fluid pressure, material balance was applied in order to estimate the original oil in place. A dynamic model was initialized and a history matching process was performed. Finally production forecasts were made considering three scenarios: a single production well, the drilling of another production well, and the implementation of a small waterflooding project.

The Blanca field is located in the lower part of the main fault Tipishca-Huaico-Blanca. Structurally it is presented as a series of nodes with a stratigraphic component and a soft structural component. The Blanca-1 well has a ten years production history, with an oil production that goes from 600 to190 oil barrels per day. The original oil in place of the Tena Sandstone, estimated by reservoir simulation, is 14.2 million barrels, and primary recovery with one well reaches 1.9 million barrels. With the drilling of an additional production well and the implementation of waterflooding, the recovery would reach 3.7 million barrels. It is considered that this reservoir may be present and be productive in other wells in this area of the Amazon basin.

The information obtained from the Blanca-1 well, and simulation models performed for the Tena Sandstone at the Blanca field, allows to recommend oil operators to investigate the characteristics of small sandy horizons presented in wells that have been already drilled and in other wells to be drilled in the future in the Oriente basin. This will provide a productive alternative in areas where traditional reservoirs have lost their initial production levels.
Resistivity Logging in Conductive-Mud Environment and High Resistivity Formations. Dual Laterolog or Propagation LWD Tool?
Authors: Lander L. A. , Silva A. , Simon C.
Published: November 2015

Volumetric estimates are required at all stages of the field life cycle. One of the main parameters used to estimate the stock tank oil initially in place is the water saturation, which depends mainly on the true resistivity (Rt) of the formation. Correct log interpretation of LWD resistivity is a challenge in the Zuata Field due to the apparent conductive invasion profile phenomenom.

This study compares the LWD phase resistivity against Compact™ Dual Laterolog resistivity curves in the same well. The section of the well was drilled with water-based mud (WBM) in unconsolidated sandstones intercalated with shale and low conductivity formations.

The geological information for this area (core analysis and image log from two neighbor wells) indicates that there are sand/shale laminations in the surrounding formation. The area where significant differences were observed among the LWD propagation resistivity curves coincided with spiral-shaped wellbore. The interbedded formation causes the electrical anisotropy and the spiral zones amplify this effect. Compact Dual Laterolog tools on the contrary, although affected by anisotropy, can be easily borehole correted to yield an accurate Rt value.

In conclusion, when the LWD data can be correctly normalized the anisotropy effect could be reduced and the LWD propagation resistivity curves may be use for formation evaluation; however, another option is to run tools that can be properly corrected by borehole size and are less affected by anisotropy and polarization such as the Compact Dual Laterolog MDL.
Durable Yet Aggressive Conical Diamond Element Bit Increases ROP by 34% Drilling Difficult Lower Chert/Conglomerate Section, Ecuador
Authors: Rodriguez R. , Laguna A. , Caselles M. Gomez , Trapuzzano R. , Gomez J. M. , Oyatomari C. G. , Ulloa P. , Chamorro D.
Published: November 2015

Drilling the intermediate (12¼-in) section in Ecuador's Oriente (East) Basin involves passing through interbedded sequences of claystone and conglomerates with chert cobbles and pebbles, which generate high impact forces that damage PDC bit cutting structures. Roller-cone bits with tungsten carbide inserts (TCIs) have been the most reliable option to drill within challenging levels that are known to chip and break cutting mechanisms; however, dedicated runs through conglomerates caused additional trips to replace bits before reaching total depth of the section. To drill the entire section, PDC bits were requested with improved cutter technology and enhanced procedures to reduce damage on cutting structures. There were events, however, of destroyed bits within conglomerates without finishing all conglomerate levels, requiring another bit to drill the entire chert level, and low ROP to mitigate cutter breakage and chipping. The operator sought a new type PDC bit that could ensure drilling the entire conglomerate intervals with enhanced ROP and longer footage for the section after the chert-composed beds.

To develop a bit solution, engineers used finite element analysis–based modeling to implement a new-type hybrid bit by strategically positioning multiple conical diamond elements (CDEs) across the cutting structure from bit center to gauge. The CDE's unique geometry applies a concentrated point load to fracture high-compressive-strength formations more efficiently than flat cutters. The combination cutting structure (CDE/flat PDC) creates a high-efficiency plowing and shearing action that improves durability yet keeps the bit aggressive enough to obtain the required ROP in lithologies found after conglomerates.

The 12¼-in hybrid CDE bit was tested in three separate wells in the Shushufindi and Aguarico fields, increasing ROP in the difficult lower chert conglomerate section compared with six direct offsets drilled with 519/616-(5 bladed PDC bits with 19-mm cutters and 6 bladed bits with 16-mm cutters) standard type PDC bits and where only one bit was used to drill entire interval considering different well profiles and used drives. In one well, the CDE bit drilled the lower conglomerate at 60.2 ft/h, 34% faster than the best offset ROP of 44.7 ft/h set with a conventional 616 PDC. The hybrid CDE bit was pulled in good dull condition (1-1) with minimum damage considering the high rpm used in the lower conglomerate.
Advanced Drilling and Logging Technologies Give New Life to Aging Fields in Ecuador by Enabling Reentry Drilling
Authors: Sanchez Jose Luis , Carrizo Hector , Salgado Janine , Ordoñez Mario , Rey Fernando , Hazboun Nidal , Laguna Alfonso , Rodriguez Rogers , Larez Aquiles , Ramirez Henry , Astudillo Pedro , Sierra Fabricio , Teran Nayda , Bastidas Marisol , Camacho Gustavo , Bastidas Alejandro , Chancay Armando , Barona David , Carrion Carlos
Published: November 2015

Excellent results from a reentry campaign developed in 2014 in Ecuador have proven the benefits of implementing new drilling technologies for reentry drilling. In this campaign, rotary steerable systems (RSS) were drivers for directional control, and logging-while-drilling tools acquired critical information while drilling. Together these tools open up possibilities for giving new life to aging oil fields and to produce from unexploited drainage zones by enabling reentry drilling.

Drilling the reentry wells in Ecuador involve using the 9.625-in. casing to open an 8.5-in. window and drilling to the geological objectives in just one hole section. For this purpose, the combination of a point-the-bit RSS system, a multi depth laterolog resistivity tool with high-resolution images, and a sourceless tool that delivers density, porosity, spectroscopy, and sigma provided 100% of directional control while acquiring comprehensive formation evaluation information in real time.

Because of the casing configuration in most of the wells in Ecuador, the most commonly used reentry option is to make the window in the 9.625-in. casing and drill the 8.5-in. hole section from the Tena formation (claystone) and Napo formation (several intercalations of claystone, limestone, unstable shales, and pay zones of sandstone). This particular configuration of formation layers is a challenge for directional control and for running wireline logs.

The use of the bottomhole assembly (BHA) with the RSS and tools described above enables successfully drilling the reentries in just one 8.5-in. run, reaching the geological targets with 100% directional control, in spite of the complexity of the well trajectory, and avoiding risks such as packoff, geometrical sticking, and differential sticking. The smoother well profile obtained by use of the point-the-bit RSS and verified through the LWD measurements guaranteed the successful run of the 7-in. liner in all of the reentries drilled in the campaign.

Reentry wells provide operators with the opportunity to have new production at less than half the cost of a completely new well and in less than half of the total execution time.

Building on this reentry campaign, continued reentry drilling will be improved with implementation of the new generation of hybrid RSS (push - and point-the-bit RSS), which will enable drilling engineers to plan trajectories to deliver greater dogleg severities (DLS). This will, in turn, enable developing deeper reentries, further reducing cost and execution time.
Comprehensive Methodology to Identify, Quantify and Eliminate the Formation Damage Mechanisms, Succesfully Applied for the first Time by the Operator in a Colombian Mature Field; Including formation Damage Modeling, Well Candidate Selection, Stimulation Treatment Design and Execution: a Case History
Authors: Nunez Garcia W. , Kleber M. , Polo R. , Franco C. A. , Escobar M. A. , Sierra A. , Arango M.
Published: November 2015

Historically, stimulation treatments made on water injector wells from a mature oil field located in the Middle Magdalena Valley in Colombia, have not been successful. This study is a comprehensive methodology of formation damage analysis performed throughdamage modeling, reservoir and water injected fluids characterization and specialized laboratory tests, to guarantee an adequate well candidate selection methodology, by identifying and quantifying the formation damage mechanisms (fines mobilization, solids invasion, emulsion formation) to achieve an optimum stimulation treatment selection.

In order to identify the formation damage mechanism currently affecting the injector wells in the field, which is believed was induced in this sensitive reservoir during the drilling/completion operations and their initial water injection stage which was developed and implemented for the first time by the operator thirty years ago, the following process was performed.

Initially, all the information available was collected and analyzed. Reservoir fluids and drilling/completion fluids compatibility tests were conducted to identify any incompatibilities; solids samples found plugging the string injection ports of the injector wells, were recovered and characterized. Cores from representative zones of the target zones were taken in order to check the mineralogy and review the damage. The possibility of mineral scaling presence, caused by the mixture of injection and formation water at down-hole conditions was evaluated, using specialized software. Then, all the data collected from the previous analysis, was used to generate a comprehensive formation damage model. The use of a geochemical simulator software which integrates numerical simulations, specialized reservoir studies, nodal analysis, mineral/organic studies and souring studies, allowed to identify and quantify the weight of each damage parameter. A 3D simulation of some of the parameters will be presented.

Having identified the induced formation damage parameters, a complete set of laboratory tests were planned and conducted to diagnose, identify and evaluate the best stimulation treatment to dissolve and mitigate the damage. An appraisal of the impact of formation/injection water salinity in the formation was done, as well as the test of formation sensibility to the fines dissolution treatments, mainly performed through the analysis of retain permeability, critical velocity and effluents, acquired in the core flow tests.

This paper will present the complete methodology and the field results of the successful application on a set of injector wells, which regain the desired water injection rate exceeding the expectations and contacting new zones to drain new oil reserves.
Chemostratigraphical Characterization of Stratigraphic Sequences: Upper B Sandstones of Eocene Misoa Formation, Maracaibo Basin, Western Venezuela
Authors: Laya A. E. , Camposano L.
Published: November 2015

The Misoa Formation (Eocene) is characterized by a monotonous succession of sandstones and shales with scarce faunal content. This unit has been divided into several operational bodies based on its lithological, electric and radioactive log character. Its rich oil content, expressed in the wells studied in the area, leads to the need for a better knowledge and understanding of its stratigraphic development, in order to enhance its exploitation. This works is focus on the upper informal units (B1, B2, B3, B4 and B5) where their lithological content of interbedded sandstones and shales, make difficult to generate accurate chronostratigraphic correlations.

Chemical analysis of 298 samples from three wells were developed to establish concentrations of major (wt%) chemical elements expressed in oxide SiO2, TiO2, Al2O3, Fe2O3, MnO, CaO, MgO, Na2O, K2O, P2O5, minor and trace elements (ppm) Ba, Ce, Co, Cu, La, Mo, V, S, Sn, Rb, Sr, Zr, Y, Cr, Ni, Pb and Zn, by using optical emission spectrometry with inductively coupled plasma (ICP-OES). In addition, mutivariate statistical analysis was undertaken to conduct chemical characterization of informal units for each well. The use of inter-elemental ratio (V/Al) and V/(V+Ni) help to define maximum flooding surfaces (MFS) and flooding surfaces (FS), allowing to confirm the MFS-43 previously defined by seismic correlation in the study area.

These results point out those B-informal units have higher geochemical fingerprint that can be chemically correlated and used in other areas of interest at this level of the Misoa Formation. This method probe to be a valuable tool, to be applied reliably statistically in siliciclastic sequences with little or no biostratigraphic control in order to reduce the uncertainty of the stratigraphic model, also this method contributes to the definition of high-frequency stratigraphic surfaces (thirth, fourth, fifth and up to sixth order).
Pressurized Mud Cap Drilling: Feasibility Study for Application in Brazilian Pre-Salt Carbonate Reservoirs and Well Control Issues
Authors: Kuehn Andrej Luigi
Published: November 2015

With the depletion of current oil reserves, drilling engineering is emerging to even more challenging environments. The pre-salt carbonate reservoirs is an example of that, now at the pinnacle of the Brazilian development projects, these reservoirs are located around 200km away from coast, in over 2100m water depth and up to 7000m below sealevel. Since the discovery of these huge fields in 2007 it was believed that the biggest challenge is to overcome the thick salt layer but nowadays drilling into the reservoir has become even more challenging. Carbonate formations are very heterogeneous and total losses are often experienced when fractures or vugs are encountered. The lost circulation in high rates can result in a well control issue if gas starts to flow into wellbore, manly it occurs due to loss of hydrostatic pressure. Pressurized Mud Cap Drilling (PMCD) is one of Managed Pressure Drilling (MPD) variations applied in situations where total or severe losses are experienced. This paper addresses a discussion regarding the application, fluid selection, safety consideration and well control issues using this technique.
Maintaining Production and Ensuring Asset Integrity Through Novel Inhibitor Chemistry
Authors: Salgaonkar Lalit , Belakshe Ravikant
Published: November 2015

This paper probes the properties of a novel naturally sourced material for the corrosion inhibition of different carbon steel alloys in the presence of mineral and organic acids as well as for the inhibition of scales. The inhibitor material is a food-grade chemical derived from a plant commonly used in medicinal formulations. It is easily available, nonpolluting, and, being of plant origin, is biodegradable. The inhibitor can be used either as a solid powder derived from the roots or as a liquid derived by means of extraction.

Corrosion inhibition of commonly used carbon steel alloy, such as N-80, was studied in the presence of corrosive media, such as 15% hydrochloric (HCl) acid and organic acid mixtures comprising acetic and formic acids, under pressurized conditions of 1,000 psi over a temperature range of 150 to 275°F. Weight loss measurements were used to evaluate the effectiveness of the inhibitor, and a corrosion loss of < 0.05 lbm/ft was considered passing grade. Evaluation of inhibitor in liquid state as a scale inhibitor was performed using the testing protocol described in National Association of Corrosion Engineers (NACE) test method TM0374-2007. The inhibition tendency toward two commonly observed scales, calcium and strontium sulfate, was evaluated, which are extremely difficult to remove once formed.

The inhibitor chemical has several N, O, and S atoms containing alkaloid structures, which enhances the capacity of the chemical for adsorption and imparts corrosion inhibition properties. At 250°F, a corrosion loss of 0.03 lbm/ft was observed with 5% inhibitor in 15% HCl acid after a test duration of six hours. At 275°F, 15% inhibitor could achieve a passing grade in three hours. With formic and acetic acid mixtures (9 and 13%, respectively), solid powder (75 lbm/gal) was tested, and a passing grade (0.02 lbm/ft2) was achieved at 275°F for six hours. The inhibitor also has certain functional groups that can trap or chelate the bivalent calcium and strontium ions and prevent the formation of scales. At 0.25% v/v inhibitor concentration, 100% inhibition of calcium sulfate and 18% inhibition of strontium sulfate scale occurred. The calcium compatibility of this chemistry exceeds the performance of most commercially available scale inhibitors. For strontium sulfate, the inhibition tendency improved to 29% when 0.5% v/v inhibitor was used.

The details in this paper align with the drive of the oil and gas industry toward greener chemistries and solutions to issues. The unique corrosion inhibition chemistry exhibited by the material is sufficiently robust to function in both organic and inorganic acid environments under challenging conditions. In addition, the same material can function as a scale inhibitor. The results show the potential for inhibiting sulfate scale as well as other commonly encountered scale.
Identification of Enhanced Oil Recovery Potential in Ecuador
Authors: Tarco J. A. , Arteaga G. R. , Merino S. Achig , Estrella J. M.
Published: November 2015

The objective of this paper is to identify the EOR potential of the Ecuadorian Amazon Region also known as Oriente Basin. The EOR methods are grouped into three: gas injection, enhanced waterflooding, and thermal. 150 oilfields and 410 reservoirs were studied as part of this work.

This study first evaluates the type of EOR method applicable to the oilfields located in the Ecuadorian Amazon Region, also known as screening. The EOR methods evaluated were:

Nitrogen injection CO2 injection Hydrocarbon injection Immiscible injection Polymer flood SP / ASP injection Steam injection, and Combustion in situ

The reservoirs analyzed for all 150 oilfields were:

Basal Tena Napo M-1 Sand Napo M-2 Sand Napo U Upper, Middle, and Lower Napo T Sand Hollin

The necessary inputs or reservoir data for this evaluation came from the Petroleum Information Databank or BIPE, a project from Secretariat of Hydrocarbons of Ecuador (SHE).

The evaluation is not detailed since the objective of this study is to provide a first guide of the theoretical potential of EOR methods in Ecuador. Those fields with more potential than others can go for further details. Due to the reservoir characteristics in the Ecuadorian Amazon Region, the most applicable EOR methods are immiscible gas followed by chemicals (Polymers and surfactants). Additional analyses should be done in order to identify the effects of the waterdrive mechanism in most of the oilfields. The CO2 miscible flood could work, but there are no near natural or anthropogenic sources. The results of this study do not cover either the economic-finance or the legal issues that can affect the implementation of the EOR technology. A second stage of a similar study should evaluate these aspects.

This study is the first work available to public based on data provided by official sources of the Ecuadorian Government. This study can be used for industry, government, and academy as guide for developing or modifying current hydrocarbon legislation.
Fluid Logging and Analysis in Real Time, an Application for Shushufindi-Aguarico
Authors: Navarrete J. , Gordon C. , Garcia M. , Bolanos M. J. , Vega J. , Lafournere J. P. , Naranjo M. , Paladines A. , Bourge J. P. , Suter A. , Henson R. , Delgado P. , Fornasier I. , Morales O. , Badillo V.
Published: November 2015

The Oriente Basin is located in eastern Ecuador at the Amazon rainforest. Shushufindi-Aguarico field is one of the most important fields in Oriente Basin with over 12% of the national production; the main hydrocarbon reservoirs are located inside the Cretaceous formations Napo and Tena. In spite of being a mature field in production since the beginning of 1970s, Shushufindi-Aguarico field still presents various formation evaluation challenges that can potentially be explored to enhance its productivity.

In order to improve fluids characterization in a recently developed area at NorthWest of the field, a new reservoir evaluation technology, Fluid Logging and Analysis in Real Time, is introduced to obtain a continuous log of quantitative composition of hydrocarbon and an improving in the pay zones analysis from gas presence in the mud while drilling.

The prospective intervals determination within the productive reservoirs is performed while drilling with cuttings analysis and chromatography evaluation in real time. This evaluation is based on Gas Ratio Method, which uses the relation between heavy, medium and light gases to identify porous rocks with hydrocarbon presence. The prospective intervals determination using Advanced Surface Fluid Logging technology gives more precision to identify thin beds by eliminating the recycled gas effect than conventional mud logging. In addition, the Advanced Surface Fluid Logging provides fluid composition in the C1-C5 range analogous to the PVT single phase composition. The fluid composition achieved in the main target zone exhibited a close correlation with a convention PVT from a recent offset well.

This paper presents a case study where ASFL technology was tested on a Shushufindi well highlighting valuable benefits, with better pay zones definition in the challenging geological environments encountered in the Shushufindi-Aguarico field. The reliability of the data provided is demonstrated by the good correlation amongst the Fluid Logging and Analysis in Real Time composition recorded in the main target zone and a recent PVT composition from a nearby offset well.
Production Optimization Based on Data Acquisition and Real-Time Monitoring Infrastructure
Authors: Mariach R. , Torres J. , Crespo C. , Gabarron R. J.
Published: November 2015

The purpose of this project is to demonstrate how the real-time infrastructure implemented by ORNCEM as a part of its automation and technical data acquisition architectures is supporting a continuous improvement for production optimization processes.

ORNCEM is responsible for Sacha oilfield exploration and production activities in Ecuador, which is the location of this project and where the entire infrastructure has been deployed and implemented, including software, hardware, telecommunications, personnel, and facilities.

The ORNCEM technical platform is based on a robust telecommunications infrastructure that provides enough accessibility for real-time data acquisition from installed devices throughout the field. Optical fiber is the technology applied to develop the industrial network to improve response time. Hardware is implemented based on the actual and future operational requirements to provide stability and scalability. Specialized applications are implemented to provide tools that help users execute complex tasks, integrate activities into workflows, and store data in a centralized repository where access can be configured based on specific requirements defined by user roles.

The oil industry has experienced drastic changes that have modified business rules, and the optimization resource is one of the parameters to evaluate efficiency in this industry. Aligned to this fact, ORNCEM is working to achieve improvement in three main areas: response time in critical situations, electric submersible pump (ESP) cycle and runtime life, and ESP performance analysis. Real-time monitoring activities enable production personnel to detect any abnormal behavior in wells that can affect production rates and to deploy a correct response for the event in record times. By evaluating ESP features and its optimal performance range and by analyzing well behavior data and well test information, it is possible to increase pump efficiency, lifetime, and runtime cycle. Also, managing electric power consumption compared with volume of fluid produced in wells and working with ESP artificial lift are important factors to determine and evaluate efficiency of production activities and to optimize cost per produced oil barrel.
Heavy Oil Reserve Development by Cycle Steam Stimulation + Gas Process in Bach-01 Reservoir
Authors: Boscán H. , Chourio G.
Published: November 2015

The Bach-01 reservoir has one of Heavy Oil Reserves (12° API) the most importan West Venezuela with an OOIP 6621 MMSTB. Stratigraphically the reservoir is comprised of Miocene sediments (Member Bachaquero, Lagunillas Fm) with a thickness of 750ft, the product of sedimentation prograding fluvial-deltaic domain, being divided into 8 intervals informal (AP, H, G, F, E, D, C, AB), which are marked differences in thickness, rock quality, facies and distribution of fluids. On the other hand, the development plan of the field horizontal wells has been based only on exploiting the upper sand (AP unit), which represents 75% of the OOIP. In this research, we have visualized and conceptualized new opportunities for development of heavy oil reserves, by optimizing steam injection in horizontal wells, through gas injection during the soaking period (CSS+GAS).

The work integrates geological and reservoir of upper-lower sands and thermal evaluation of the optimal parameters of steam injection and rock-fluid characterization. In this research were used field data for making model pit that is the representation of the behavior of production wells, subjected the process of css+gas and weighted data reservoir, for performing a pseudo-compositional thermal simulation black oil system, through which were evaluated the effects caused in the reservoir, by css+gas process. The most outstanding results concerning this process were: increase oil accumulated by cycle, increased volume of the steam chamber in horizontal wells and, decreased viscosity.