The new challenges of the oil exploration focused to the location in closed traps against faults in deep waters. The methodology has been developed for the juxtaposition studies by faults in structural traps that it analyzes the sealed surface, which is like an evaluation technique that quantifies of efficient way, the exploratory risk related with the sealed and the hierarchy of the prospective objectives in an opportune way speeding up the answer capacity for the taking of decisions that imply a high consumption of time and money. This summary synthesizes the method for the construction of the Allan's diagrams of juxtaposition. It consist of using computational tools that optimize the times of elaboration. The work flow has been directed in the realization of the juxtaposition (2D/3D) diagrams that it allows to evaluate the efficiency of the lateral sealed in traps against fault segment and obtaining of hydrocarbon new wells. To determine the capacity of sealed for the faults the seismic interpretation it is needed in depth of the roof-ceiling horizons, as well as the behavior of the segments of faults. Later on, it is carried out the seismic mapping of each geologic element to analyze. The principal stage of the methodology is the obtaining by means of an operation vector subtraction of the intersections of the objective horizon so much of the roof block and the ceiling block on the fault surface in the setting. Once certain, the vertical component of the fault jump for each one of the exploratory objectives. It proceeds to elaborate Allan's (2D) diagram in a profile made
up of the integration of the intersections of all the objectives for each contour of fault surface. Finally, It spreads in perspective the geometry 3D of each fault plan with their intersections type and their impact in juxtaposition. This method has been proven with success in the hydrocarbon locations on deep waters of area the Region Marina from Gulf of Mexico.
The geological structures to drill and reach the producing reservoir of the South region of Mexico are very complex. They can vary from deep fractured carbonates reservoir at more than 7000 m true vertical depth, anticline uplifted by salt or/and shale dome themselves inducing abnormal pressure up to 2.2 gr/cc of equivalent density in the overlying formation. The geological complexity of the south region is reflected also in its geo-pressures, geo-stresses and geomechanical properties.
Since early 2000 Petróleos Mexicanos (PEMEX) has considered the Geomechanics discipline as a key component for their future economic success. With the urgent need to improve recovery, more complex wells are being drilled and PEMEX has taken the challenge to have geomechanics analysis for any well that will cost more than 10 Million of dollars. This strategy has been translated with training of key personnel, geomechanical core campaign and geomechanics studies included into their drilling program. Since 2006, more than fifty geomechanics studies (analytical and numerical) have been carried out in the south region of Mexico and have been incorporated to mitigate drilling risk and optimize well design. Velocity analysis, Geomechanics core test interpretation, caving interpretation, breakouts and induced fracture analysis from image logs, direct pressure measurements, leak off test and mini-frac interpretation are some of the different information used to calibrate the geomechanics studies.
This paper refers to the regional compilation, findings and results of the 50 geomechanics studies conducted in the different fields of the south region between 2006 and 2010 and its impact on the well design of exploratory and development locations. The paper presents to the industry, the methodology used for their construction, illustrated by the data used for their calibration and how they were successfully used for well design and real time decision with selected post mortem analysis for some well. Finally the results of the geomechanical studies (Strength, overpressure and stress anisotropy) have been mapped regionally to forecast the geomechanics behavior in the entire south region of Mexico to optimize the drilling of future well locations.
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.
The production of heavy and extra heavy crude by dilution with lighter hydrocarbons produce volumetric differences, which are associated to diluent losses attributed to volatilization phenomena. This article present results of the production data analysis from different fields of heavy and extra Oil in Colombia, where the assessment of models for determine the shrinkage factor in mixing process of heavy crude oil with diluents were incorporated.
To develop this work, a model to predict the volume shrinkage occurring in heavy light oil mixtures was defined. The analysis was conducted with 25 types of crude oil and 11 diluents, their mixing properties of viscosity and API gravity were measured and calculated. Several authors have proposed models to determine shrinkage factor (Erno, Booker and API). Those models were evaluated with production data, then using multivariable regression techniques an adjusted model was proposed, Results shown the fraction of diluent and the value of the difference between the inverse of the densities of oil and diluent are the important variables in this new model. \Finally the model was incorporated in the volumetric production balance of these fields.
Chokes are used to limit production rates to meet sale contract, comply with regulations, protect surface equipment from wearing out, avoid sand problems due to high drawdown, and control flow rate limited by capacity of the facility. Single gas phase flow through choke is vital to oil industry because not only an accurate estimation of gas flow rate guarantees a reliable supply to the end users, thus the predictable revenue from gas sale for the company, but also protect the equipment from breaking as a result of high gas rate. Nevertheless, importance of gas metering cannot be overemphasized. Gas flow through choke had been studied by numerous investigators, Different choke flow models are available from the literature, and they have to be chosen based on the flow regimes, that is, subsonic or sonic flow. The most common used flow equations developed by Shapiro, Zucrow and Hofmann are used for subsonic and sonic flow, respectively. Sonic flow happens when downstream to upstream pressure ratio is equal to critical pressure ratio.
A careful review of these equations indicated that they are not theoretically rigorous and give inaccurate gas flow rate for the real gas. Thus these equations need to be modified in order to be used to calculate gas flow rate under both flow regimes. After a thoroughly analysis and derivation we came up with equations that have solid base. New correlations that reconcile the issue caused by approximation method used to derive the old gas flow equations were based on both engineering judgment and physical phenomenon. The error in the old equation can be corrected with the new equations. New equations provide good approaches to quantify gas flow through choke.
Knowledge of pore fluid pressure is essential for safe drilling and efficient reservoir modelling. An accurate estimation of pore pressure allows for more efficient selection of casing points and a reliable mud weight design. Current commonly used methods of pore pressure prediction are based on the difference between a ‘normal trend' in sonic wave velocity, formation resistivity factor (FRF), or d-exponent (a function of drilling parameters) and the observed value of these parameters in overpressured zones. The majority of the techniques are based on shale behaviour, which typically exhibits a strong relationship between porosity and pore fluid pressure. However, carbonate rocks are stiffer and may contain over-pressures without any associated influence on porosity. Indeed, the application of common pore pressure prediction methods to carbonate rocks can yield large and potentially dangerous errors, even suggesting absences or decrease in abnormal pressure in zones of high magnitude over-pressure. In some cases, the hypothesises which been in the conventional methods seems to be flawed in some cases where pore pressure decreases by depth.
In this research, a new method for effective stress calculation has been obtained using the compressibility attribute of reservoir rocks. In the case of over-pressure generation by undercompaction (as occurs in most clastic over-pressured sequences), pore pressure is dependent on the changes in pore space, which is a function of rock and pore compressibility. In simple terms, pore space decreases while the formation under goes compaction, and this imposes pressure on the fluid which fills the pores. Carbonate reservoirs in two fields in Iran have been investigated to establish pore fluid pressure generation mechanisms, and to attempt new methods for pore pressure prediction in carbonate rocks.
The understanding and mitigation of downhole vibration has been the subject of intense scientific research in the drilling industry in recent years, as inefficient drilling results in slower and more expensive operations. In order to drill ahead, a sufficient amount of energy must be supplied by the rig to overcome the rock strength, the reactive torque of the drilling system, drag forces, fluid pressure losses, as well as the energy lost by way of downhole vibrations.
It has been well documented that downhole vibrations are a significant drain on the amount of effective drilling energy available to the bit. When the drill string enters resonant modes of vibration, not only does the drilling efficiency decrease, but the likelihood of catastrophic drill string component failures increase. The amount of destructive energy expended in these resonant modes of vibration, when left unchecked, may overcome the material limits of components in the drill string. In this sense, the mitigation of downhole vibrations will result in faster, smoother, and cheaper drilling operations.
Software using Finite Element Analysis (FEA) has been developed to understand these vibration phenomena and to predict which combinations of drilling parameters should result in more efficient drilling. The software graphically presents the results, depicting undesired levels of resonant vibration produced with specific drilling parameter combinations, based on the BHA geometry and wellbore design. Predictions made by this software have produced notable results, including a world record for Rate of Penetration (ROP) in the Gulf of Mexico.
This paper also examines different Bottom Hole Assembly (BHA) designs and the resonant vibration modes that may be initiated while drilling, using the proprietary software package. The combination of proper BHA design and the correct selection of parameters results an overall improvement to drilling efficiency. A variety of case studies from Latin America, incorporating the results of the vibration analysis, will demonstrate solid improvements to drilling operations in terms of time and cost savings, increased penetration rates, and improved dull conditions. The use of field validated software for vibration prediction and mitigation has a potential role in the drilling industry as important as the introduction of PDC bits in the 1980s.
Reservoir fluids from Lake Maracaibo have reportedly caused asphaltene operational problems ranging from plugging of wellbores, pipelines and flowlines to clogging of surface facilities (Garcia et al, 2001). Production of fluids from some part of the region has been dramatically reduced due to asphaltene precipitation and deposition (Vasquez, 2010).
Asphaltene and wax precipitation is a serious problem in production, transport and processing of reservoir fluids. Of particular concern are the effects of asphaltene precipitation and their potential to disrupt production due to deposition in the near-wellbore regions and production tubulars. This phenomenon is directly influenced by changes in temperature, pressure and composition. Commonly, low temperatures increase the probability of asphaltene precipitation; however, experimental studies on the fluid under study demonstrated unusual asphaltene phase behavior.
This project involved experimental studies on fluid phase behavior as part of a formation damage investigation. The main challenges with fluids from the Maracaibo area are the relative high H2S content (1-3%), high reservoir temperature (270°F) and the asphaltenic nature of the crudes.
In this study, the asphaltene precipitation envelope was determined using Near Infrared (NIR) Solid Detection System (SDS), High Pressure Microscope (HPM), Particle Size Analysis (PSA) and gravimetric techniques.
As expected, a significant amount of asphaltene was observed to precipitate during depressurization. However, reversibility of the precipitated asphaltene was also observed below the bubble point and during re-pressurization.
What was unusual about this fluid was the unconventional asphaltene precipitation onset conditions found at low temperatures. For most crude oils worldwide, asphaltene precipitation onset pressure increases at lower temperatures; however, the fluids considered in this work have shown a non typical behavior wherein the asphaltene onset pressure decreases with decreasing temperature. Such behavior was earlier presented by Ting et al, 2003 on the Maracaibo oils; however, no reports have been published since.
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.