Given the high degree of uncertainty in the oil industry present production development projects, the use of probabilistic models is of considerable interest as a means to support decision making. Besides that, there is a constant pursuit to optimize oil drainage, to maximize reserves as well as the financial outcome of the project. A robust study, characterizing the uncertainty of the various critical parameters, such as number of wells, maximum water injection rates, relative permeabilities and rock and PVT data, is of paramount importance to assure that the impact of all uncertain parameters have been accounted for.
The present risk curve construction methodology takes into consideration uncertainties in the geological model and in the dynamic properties in an integrated manner. Six geologic scenarios with distinct permo-porous distributions were generated. A study was conducted to obtain PVT correlations of the produced fluids.
A sensitivity analysis was performed to eliminate non-significant parameters. The relevant ones were well adjusted to the production data in all geologic scenarios. Optimum exploitation configurations were obtained for each model, using the net present value (NPV) as an objective function. Each configuration was applied to all scenarios and the estimated monetary values (EMV) of each configuration were calculated. The maximum EMV was used as optimum criteria. The final product obtained was a development strategy risk curve, showing the viability of the proposed methodology.
Fluid losses are still today one of the most challenging problems in well construction. Most strategies to control losses are empirical and in some situations, detrimental effects can not be avoided. This article deals with unique modeling efforts to understand the dynamics of bridging fractured zones. The main tools adopted to address the problem were the Computational Fluid Dynamics, whenever necessary coupled with Discrete Element Method packages. The main goal was to study particle deposition inside fractures due to losses through the external walls of an axial annular flow. ANSYS FLUENT® and EDEM® were the adopted simulation tools.
The study includes two different modeling strategies: Discrete Element Simulation and Granular Eulerian CFD approach. The first method solves the particle trajectory equations individually, considering collision and cohesion effects. Despite of the reliability of the approach, computation effort is huge and limits the number of particles in the system. The Eulerian approach, on the other hand treats statistically the particulate system, generating a probabilistic field of occurring one or the other phase at given space and time. This approach obviously generates smaller computational costs. The developed methodologies allow the evaluation of the efficacy of bridging agents in plugging fractured zones.
High energy electron particles were utilized to improve the rheological properties of heavy asphaltic petroleum fluids and upgrade them into lighter, and more utilizable, fluids. Heavy oil reserves, as one of the most abundant sources of energy, have attracted considerable attention during the last decades. However, high viscosity of such fluids always poses problems during production and transportation operations. Complex hydrocarbon molecules in heavy petroleum fluids can be affordable sources of energy if we can find a way to convert them into components of simpler structure in a cost-efficient process. While high energy demand of conventional thermal and thermo-catalytic process casts doubts on the application of such methods, emerging electron beam upgrading technology appears to provide promising achievements as a novel hydrocarbon treatment process. Radiation thermal cracking was observed to reduce the viscosity of highly asphaltic petroleum samples more than the conventional thermal cracking method. Simulated distillation analysis showed higher concentrations of lighter components in radiolyzed samples, which indicated the intensified cracking as a result of electron irradiation. Stability of the products with time is one of the main concerns because samples with altering properties may cause difficulties after the upgrading process. The viscosity of thermally cracked samples showed a substantial increase with time, while aging investigations on radiation thermal cracking products demonstrated stable properties.
Restrepo, Alejandro (Equion Energia Ltd.) | Ocampo, Alonso (Equion Energia Ltd.) | Lopera Castro, Sergio Hernando (U. Nacional de Colombia) | Diaz, Maria Paula (U. Nacional de Colombia) | Clavijo, Julian (Equion Energia Ltd.) | Marin, Jefferson (Universidad Industrial de Santander)
Well stimulation for production or injection enhancement in mature fields is a key and challenging task. Loss of reservoir energy due to pressure depletion coupled with complex damage scenarios existing in adverse petro physical environments can become restrictive factors for the proper performance of conventional liquid based chemical stimulation systems. Main limitations are normally related to high interfacial tensions preventing optimal well´s clean up and cost-effective achievable penetrations. This work presents a new well stimulation concept in which the carrying system is gas instead of liquid. The overall study will be presented in 2 parts. Part I will discuss basic physical questions related to treatment durability as a function of deployment method (continuous dispersion vs liquid batch gas displacement) for at least two damage scenarios of particular interest: asphaltene deposition and condensate blockage. A basic mechanistic simulation is also presented for benefit estimations at well scale. Part II will focus on field trials design and execution using micellar and/or fluoropolymer type of chemistries that exhibited the best performance when tested under laboratory conditions.
Experiments herein presented were done in formation sandstone cores simulating reservoir conditions. It is shown that natural gas when used as the carrying system to deploy conventional asphaltene dissolution and condensate removal chemistries enhances both Ko re-establishment and treatment durability as compared to equivalent liquid-based applications. Additional studies are being performed to maximize the effectiveness of the GaStim concept. Sensibilities to gas type (N2, CO2), added chemical and dosages as long as field trial documentation will be presented in part II of the present work. GaStim concept is presented as a novel chemical stimulation technique potentially allowing deeper penetrations and better chemical adsorptions. Its potential, although still not fully undiscovered, is certainly supported by higher Ko reestablishment values and longer treatment durabilities observed.
Andrade, Alexandre Victor (Schlumberger) | Torres, Lenin Omar Diaz (Schlumberger) | Bermudez, Raul (Schlumberger) | Bedino, Henry Daniel (Schlumberger) | Carrillo, Nixklafe Neil Atencio (Schlumberger) | Vargas, Candelario (Schlumberger) | Carrillo, Angel Pedro Gonzalez (Pemex) | Martinez, Ignacio Ramirez (Pemex)
Lost circulation is a major problem when drilling oil wells in Southern Mexico, where depths normally reach up to 7,000 meters with a fractured carbonate reservoir as the target. Very high mud losses reduces rate of penetration, increases cost of
materials and induces other unwanted drilling events. Many times operators and service companies are forced to apply in-ahurry lost circulation treatments mostly based on trial and error with very mediocre success.
A Fiber system has been developed to cure lost circulation caused by the presence of natural fractures. The fiber system is deployed either in a spacer ahead of cementing or by spotting a pill during drilling. This Fiber system disperses readily in
water-base fluids and is fully compatible with standard surface mixing and pumping equipments.
This field study presents the application in Mexico of this innovative and resilient Fiber lost circulation system designed to mitigate the lack of characterization of the loss zone. Fourteen jobs performed and two applications described include
pumping through commonly used BHAs during drilling, and as part of the spacer ahead of the cement slurry, when partial or total losses occurred with casing on bottom.
Implementation of this engineered fiber-based lost circulation solution was extremely successful compared to the average success of other similar purpose systems. Particularly, two features were considered a breakthrough in applications while
drilling: first, this solution saved 15 to 24 hours of rig time per operation as the BHA needs not be pulled out; and a second, and perhaps more important advantage consisted in being able to resume drilling quickly after pumping the material without
risking to destroy the integrity of the seal. When used in a spacer ahead of cement in wells, where circulation was lost after getting the casing to its landing depth, the Fiber lost circulation solution allowed to successfully getting top of cement at the
planned desired depth ensuring effective zonal isolation.
Introduction: Lost Circulation
Even over more than 60 year of drilling, lost circulation is still characterized as one of the major issues that lead to undesired non-productive time (NPT) in drilling operations.
Lost circulation (LC) is defined as the partial or total loss of drilling fluids into the formation; it can take place while drilling, tripping into the hole, running casing or cementing. (Nayberg and Petty, 1986).
There are two categories for losses: natural and artificial (induced) (Wang et all. 2005). Natural losses can occur due very permeable formations, large pores, vugs, leaky faults, natural fractures; artificial or induced losses occur when the pressure
exerted in the formation is greater than the formation can contain. Fractured formations are responsible for most severe lost circulation cases.
In this paper, we present our work on developing parallel preconditioners for iterative linear solvers on NVIDIA Tesla GPU. A unified triangular solver for ILU-like preconditioners is developed. A new matrix format and the corresponding parallel algorithm are designed. Based on this triangular solver, block ILU(0), block ILUT and domain decomposition preconditioners are implemented. Numerical experiments show that these GPU based parallel preconditioners are around 8 times faster than our CPU based preconditioners.
Florez Anaya, Alberto (Pacific Rubiales Energy) | Araujo, Ysidro Enrique (Pacific Rubiales Energy) | Uzcategui Rivas, Myriam Elizabeth (Pacific Rubiales Energy) | Parra Moreno, Wilson (Pacific Rubiales Energy) | Lavado Quinones, Rosa (Pacific Rubiales Energy)
The purpose of this paper is to report the methods used and results of the Rubiales Field development, located onshore in "Los Llanos?? Basin in Colombia. Horizontal well technology was used to drill through unconsolidated sandstones with an active and strong aquifer, under primary heavy oil depletion with an oil gravity ranging from 11.3 to 14.4 °API. Horizontal wells allow oil production rate increases, water production delays, oil recovery factor increases, and sand production decreases.
The Rubiales Field has an OOIP of 4,608 million STB oil, and a wide reserves volume of 385 million STB oil was certified in June 2011 with horizontal well technology. On 31 December 2011, the cumulative oil production of the field was 163 million STB oil (3.7% recovery factor). Currently, the oil production rate is 180.3 thousand BOPD, of which 159.6 thousand BOPD (88.5%) come from horizontal wells.
The actual operator company has implemented an aggressive campaign, drilling over 296 horizontal wells from 2006 to 2011. Since 1981, 202 vertical wells and 7 deviated wells have been drilled. In Areniscas Basales Unit, the average production rate reached a peak of over 2,000 BOPD for each completed horizontal well. This production rate is almost 7 times that of the neighboring vertical wells production.
The placement of the producer horizontal wells has been optimized in the Rubiales Field in locations where the net pay is less than 30 feet by implementing the use of the azimuthal resistivity log, which allows for real-time mapping while drilling up to a distance of 20 feet. In December 2011, 27 horizontal wells were drilled using this technology. The global production rate for these wells is currently 17.5 thousand BOPD.
Because of the success of these horizontal wells, the operator company also implemented this technology at the Quifa Field, discovered in 2008, which is an extension of the Rubiales Field. The oil production rate at the Quifa Field in December 2011 was 39.4 thousand BOPD.
One adequate management and optimization of mature fields requires the use of techniques, methodologies, technologies and analysis of the behavior of the wells to generate recommendations of production optimization with the highest probability of exit.
One alternative that today has proven successful and is widely applied worldwide to maximize the profitability of the fields, consists in the implementation of hydraulic fracturing jobs, to improve the flow capacity of the wells, which is achieved to go through the formation damage, speeds up the reserves, etc.
However, one of the main difficulties of hydraulic fracturing, are the high friction pressure losses in the near wellbore (NWBF), which require high pressures to break the formation and equipment of higher power in surface. This means work over more expensive and with a lower economic profitability.
An evaluation of new technologies, allowed the identification of the alternative called High Energy Gas Fracturing (HEGF), as a pre-fracturing technique to reduce pressure losses by friction in the near wellbore (NWBF). HEGF is a perforating technique with propellants, which not detonate, but they blaze with high heat, but unexploded (deflagrate), releasing a high energy gas that reaches a sufficient pressure pulse (10,000 to 50,000 psi) and combustion time (5 - 30 milliseconds) that creates fractures in all radial directions at short distance.
For different operational areas of the Colombian state owned oil company, Ecopetrol SA, was performed an evaluation of pressure loss by friction in the near wellbore (NWBF), during hydraulic fracturing operations that have been executed. This allowed to make recommendations to implement HEGF and thus optimize the hydraulic fracturing operations. This paper presents the results of the assessment in the fields Apiay, Austral, Gavan, Suria and Yarigui.
Finally, the main findings, conclusions, recommendations and field results obtained in this study are shown.
One of the greatest strategic focuses of the oil industry is the maintenance area, which is directly responsible for the availability of equipment involved in the production process. It affects the platform operational efficiency and consequently, the company results. Those results will increase with increases in effective maintenance management. In addition, the oil industry has experienced a wave of process optimization and systematization through new tools that support management and decision-making processes.
This paper presents a workflow that enables remote monitoring of onboard equipment status (operating, stand-by, or unavailable), identification of equipment with elevated risk of target violations, and the calculation and analysis of availability indicators. It also provides access to the historical data of unavailability events for the equipment monitored. This workflow performs real-time equipment monitoring through several logic implementations using sensor signals,
automatically recording events at the moment that the equipment shows to be unavailable, and sending alerts to personnel responsible for the equipment. In addition, some equipment that do not have sensor signals, which enables real-time monitoring, were included in the daily routine through a manual process of entering unavailability events in the system enabling a further analysis of the historical unavailability. Consequently, the availability indicator is calculated in real time on the basis of these unavailability events. During the monthly indicator consolidation process, the system generates a report of the equipment that functioned below the set target, enabling a focus on the treatment of the most critical equipment during maintenance and asset integrity meetings.
The workflow solution provides several benefits. First, it monitors the status of equipment in real time, enabling a faster return to normality. It also captures unavailability events automatically, and records and provides details about these events. The workflow also monitors availability indicators, monitors major unavailability events by exception and historical analyses, and ensures the integrity of the process plant.
The first formation testing tools were introduced as wireline tools in the 1950s. Since then, many technological steps were achieved, starting with simple sampling devices adding different measurement technologies in the 1980s up to formation pressure while drilling (FPWD) tools introduced to the field in 2000. Over the last 20 years wireline technology evolved towards high??quality single??phase sampling that also led to the development of the first formation sampling while drilling (FSWD) tools being introduced just over a year ago.
In this paper we present a new fluid analysis and sampling tool designed for logging while drilling (LWD) applications. As it is built on the widely proven FPWD technology, it includes all its functionality of optimized testing and seal control.
This service operates using a closed??loop control system, integrates real??time downhole analysis of the pressure data, and provides a repeat pressure test with an optimized rate control based on the in??situ derived mobility. This is made possible by the highly accurate pump control system employed. In addition to pressure and mobility capabilities the fluid analysis and sampling tool can analyze and obtain formation fluid samples. The new tool is equipped with high??power pump??out capabilities and highly sophisticated sensors to measure the optical refractive index, the sound speed, the density and the viscosity of the fluid. The innovative pump control prevents alteration of the fluid sample by avoiding pumping below the bubble point.
The tool employs the same sample tanks that are used in our wireline tools. The tanks are approved by the Department of Transportation (DOT) for direct transportation of a sample to a certified pressure??volume??temperature (PVT) lab without transferring the sample into another sample bottle. The tool can collect and preserve up to 16 single??phase samples at surface pressures up to 20,000 psi in a single run. It uses a nitrogen buffer system to ensure the suffienct pressure is applied to the sample to prevent alteration.
In this paper the capabilities of this new LWD fluid analysis and sampling tool and its first field application on a land rig in Oklahoma are be shown. The field results are compared with a wireline results run to prove the concept of shorter clean??up times while sampling soon after the formation is penetrated by the drill bit. An outlook will be given how to apply this new technology in future applications.