A recently developed logging-while-drilling (LWD) ultrasonic imaging tool has been field tested and shown to provide high-resolution images that give an early indication of problems during drilling operations. These images are compared to other LWD imaging techniques in oil-based muds to demonstrate the advantages of the new technology.
The new tool employs a system of three equally spaced ultrasonic transducers along the circumference of the tool at the same level. This arrangement provides the high data density needed for the images and enables precise location of the tool in the borehole for accurate borehole corrections to the data, thereby enhancing the overall image quality. The images are used with other real-time LWD and measurement-while-drilling (MWD) measurements such as equivalent circulating density (ECD), and formation pressure tests (FPT), to monitor wellbore stability and other issues that can lead to non-productive time (NPT) during drilling operations.
The new tool has been field tested in a number of wells in different parts of the world. These tests demonstrated the capabilities of the images to identify wellbore stability issues such as breakouts and cavings. The images can also be used to identify geologic features such as fractures and faults that can impact the drilling operation as well as the eventual production of the well. Examples will also be shown that combine the interpretation of the images along with other MWD and LWD measurements to provide a superior technique for wellbore stability management in real time.
The new LWD tool provides high-resolution borehole images in oil-based and water-based mud systems. Previously, high-resolution images from an LWD tool were only available in water-based mud systems using electrical imaging tools. This new technology provides a much clearer image of the borehole that has been available in the past. The techniques developed for using this information in real time reduce the frequency and magnitude of borehole-related NPT events.
Sediment profile imaging (SPI) technology characterizes
The SPI camera works like an inverted periscope and obtains an undisturbed 21x15-cm cross-sectional image of the upper sediment column. The camera is internally powered and can be deployed rapidly from a standard winch in depths to 4,000 m. Many stations can be sampled in a single day by "pogo-sticking" across a survey area. Sediment grain size, penetration depth, surface boundary roughness, natural and anthropogenic depositional layers, depth of the oxidized surface sediment layer, maximum biogenic mixing depth, and infaunal successional stage can be directly measured at sea or immediately following the cruise. Final SPI data sets can be provided within a few weeks of the survey.
Details on the features measured in SPI images and the underlying interpretive paradigms are presented. To standardize the SPI data generation process, Integral Consulting Inc. has developed 1) a semiautomated image analysis platform, and 2) a SPI data-specific database architecture that allows both numerical and non-numerical metrics to be incorporated into a standard database structure. An integrated, software-based SPI analysis platform has been developed that imports image files and metadata and provides a graphical user interface. The software automatically stores the data, which can then be reviewed for quality assurance, plotted, statistically analyzed, and mapped or exported to other platforms (e.g., Esri ArcGIS©) for further evaluation. Image processing algorithms have been developed using a combination of open-source and commercially available software packages (e.g., MATLAB® and OpenCV) to automatically quantify key parameters.
SPI technology’s underutilization in the oil and gas industry may be in part due to a lack of standardization in the measurement of basic features in SPI images. A primary objective of this work is to develop a streamlined, standardized, and transparent process for generating and managing SPI data.
It is well established that polymers are successful drag reducers due to their viscoelastic properties that can suppress the turbulence eddies and fluctuations and hence, reduce friction pressure losses. Various factors can affect the polymers’ drag reduction characteristics such as polymer type, concentration, shear degradation, and flow geometry. However, few studies have shown the effects of salt type and concentration on drag reduction characteristics with almost no studies discussing their effects in the light of the ionic strength. The ionic strength is considered a more widespread scale to quantify the effects of salt contents on a specific characteristic. This study is undertaken to better understand the relation between ionic strength and drag reduction performance of polymers in straight tubing.
For this purpose, two widely used anionic AMPS copolymers; Nalco ASP-700 and ASP-820, are investigated. The salt matrix includes 2% KCl, 4% KCl, and synthetic seawater. For synthetic seawater, different recipes exist. The recipe adopted includes 1.0 lb/bbl Na2SO4, 10.5 lb/bbl NaCl, and 0.4 lb/bbl CaCl2. A ½-in. OD flow loop with a 15-ft. straight tubing section is used.
The results show that drag reduction behavior is better correlated with the solution ionic strength, and not the salt concentration. Higher ionic strength yields lower drag reduction despite the lower salt concentration. However, the adverse effects of salt and its ionic strength diminishes as higher Reynolds numbers. Both ASP-700 and ASP-820 exhibit a very effective drag reduction behavior and their performance is significantly affected by the polymer type, shear rate, and salt content. Correlations between ionic strength and drag reduction ratio for both polymers are proposed. The correlations exhibit a reasonable agreement with the gathered experimental data. They can be used to quantify the adverse effects of different salt types and concentrations on drag reduction characteristics of polymers in straight tubing
Improving Well Control Process Safety: A Second BOP, or is There a Better Way?
Liria, Juan (Fugro) | Coelho, Henrique (Fugro) | Sproson, Dave (Fugro) | Martinho, Paulo (Fugro) | Webb, Cody (Fugro) | Oropeza, Fernando (Fugro) | Bradon, Jill (Fugro) | Smith, Rosemary (Fugro) | Peng, Zhong (Fugro)
Accurate, reliable and cost effective hindcast databases have become essential tools for the design of offshore and coastal structures. Within the Gulf of Mexico (GoM), many databases exist, which cover operational wave climates, but very few of these fully resolve the complexities of Tropical Revolving Storms (TRS) in terms of both the spatial and temporal resolution. Here, we present the results of our hindcast analysis, covering all TRS affecting the GoM from 1979 to the present. This database represents all the physical and dynamic aspects of the TRS, reproducing not only the cyclonic winds, but also how the hurricane interacts with the atmospheric mean flow in the area surrounding the eyewall. The Weather Research and Forecasting model (WRF-ARW), with two nested fixed domains (18 km and 6 km), and uncoupled Hurricane WRF (HWRF) have been used to model the atmospheric conditions. Waves have been modeled using Wave Watch III (WW3), a third-generation wave model, driven by the 18 km WRF modeled winds. Boundary conditions from our inhouse global wave database have been used, forced by CFSR winds. Most of the existing databases produce a set of TRS based on the records of wind, track, pressure and radius of maximum speed, producing a uniform field of wind and pressure. We have developed a state of the art wind and wave database of TRS based on fully convective, non-hydrostatic numerical models. Model results have been validated against observational data from buoys, meteorological stations, airborne measurements, satellite data and against tracks from the International Best Track Archive for Climate Stewardship (IBTrACS) database. Results show that the modeled TRS are quite sensitive to the initial state, obtaining the best results when initializing the model with the vortex in a mature state. The hurricane intensification and wind distribution are well reproduced by the HWRF model, being in good agreement with both the track and measurements. This approach provides a realistic, cost effective and up to date hindcast of the wind and wave conditions during hurricane events throughout the GoM. Using cutting edge models, we have been able to reproduce hurricane conditions over the whole GoM, obtaining results that are physically representative.
Understanding the stimulated reservoir volume and mapping hydraulic fractures away from the wellbore remains one of the biggest challenges in unconventional plays development. Currently available production logging and tracer technologies have shallow depths of investigation—only a few inches beyond the wellbore. Far-field microseismic mapping offers an image of micro-earthquakes that are caused by shear slippage during a hydraulic fracture treatment. Although the location of the associated microseismic events enables spatial mapping of the stimulated rock volume, particularly its orientation and growth characteristics, the microseismic deformation does not provide direct information about hydraulic fracture effectiveness.
The latest improvement in deep shear wave imaging processing (DSWI) provides a visual representation of geological features up to 100 feet from the wellbore. DSWI nicely fills the resolution space between conventional near-wellbore diagnostic technology and far-field microseismic mapping. The shear wave azimuthal sensitivity enables estimation of the hydraulic fracture geometry away from the wellbore. It also provides direct visualization of the actual reservoir volume that has been stimulated in the mid-field region with the extension of hundreds feet from the wellbore.
This paper presents a case study of the post-hydraulic fracture diagnostic in a shale reservoir using deep shear wave imaging technology. The information derived from the pre- and post-hydraulic fracture imaging enables a better understanding of the stimulation treatment effectiveness and fracture propagation away from the wellbore. This imaging can also be used for the completion optimization of the new drilled wells, as well as for the identification of previously unstimulated zones for re-fracturing.
The accuracy and credibility of the DSWI hydraulic fracture diagnostic was confirmed by running a cross-dipole acoustic log in a well with high water cut. Radioactive material present in the produced water caused up to 150 API increase in the gamma ray activity due to precipitation associated with the pressure drop in a hydraulic fracture. The study showed that the lateral intervals with a substantial increase in gamma ray activity matched the hydraulic fracture locations identified by the DSWI process.
These case histories highlight the value of the information obtained from the DSWI to enhance the fracture optimization, to improve ultimate recovery, and to reduce overall operational cost.
Vipulanandan, C. (Center for Innovative Grouting Materials and Technology and Texas Hurricane Center for Innovative Technology, University of Houston) | Maddi, A. R. (Center for Innovative Grouting Materials and Technology and Texas Hurricane Center for Innovative Technology, University of Houston) | Ganpatye, A. S. (Stress Engineering Services)
During the installation of oil and gas production wells, it is critical to have a successful cementing operation. The quality of the cementing job strongly depends on the cleaning efficiency of the spacer fluid in removing not only the drilling fluid with the cuttings but also the filter cakes during the drilling operation. Based on the depth applications, different types of spacer fluids are used in the oil gas industry. In this experimental study modifying the smart spacer fluid properties in-situ was investigated. Optimization of spacer formulation was carried by having material properties such as density, rheology and cleaning efficiency as the variables. In this study, using the maximum shear stress tolerance of the spacer fluid determined using the Vipulanandan rheological model was investigated to quantify the cleaning efficiency of the spacer fluid.
In this study, the effects of pressure, temperature and magnetic field strength on the electrical resistivity and rheological properties of a sensing smart spacer fluid modified with iron oxide nanoparticles (nanoFe2O3) were investigated. The temperature was varied from 25°C to 75°C. The magnetic field strength was varied from 0 T to 0.6 T. The nanoFe2O3 contents (particle size of 30 nm and surface area of 38 m2/gm) in the spacer fluid were varied up to 1% by the weight of spacer fluid to enhance the sensing and rheological properties of the spacer fluid. The initial resistivity of the spacer fluid without any nanoFe2O3 at 25°C was 0.2 Ωm. Addition of 1% nanoFe2O3 increased the electrical resistivity by 3.5%. Adding nanoFe2O3 enhanced the piezoresistive behavior of the smart spacer fluid. The electrical resistivity changed by 0.7, 5 and 12% for the spacer fluids with 0,0.5% and 1% nanoFe2O3 respectively for a maximum pressure of 500 psi. Increase in the magnetic field strength improved the rheological properties while increasing the temperature decreased the rheological properties of the spacer. The rheological properties of the spacer fluids were characterized by high strain rate to determine the nonlinear behavior of the shear thinning spacer fluid. The spacer fluid rheology was modelled using Bingham-plastic model, Herchel Bulkley model and Vipulanandan model. The electrical resistivity was used as sensing parameter to monitor the percentage of oil cleaning efficiency of the spacer fluid. Based on the new Vipulanandan rheological model, the yield stress (τo) of the modified spacer fluid increased by 6% to 100% depending on the oil content, nanoFe2O3 content, temperature and magnetic field strength. The maximum shear stress tolerance (τmax) for the spacer fluid increased from 49.4 Pa to 65.5 Pa, 33% increase at the temperature of 25°C with 1% addition of nanoFe2O3. The cleaning efficiency of the spacer fluid in removing oil based drilling fluid contamination was 79.8% without the addition of nanoFe2O3. With the addition of nanoFe2O3 the cleaning efficiency increased from 79.8% to 99.4%, 20% increase in the efficiency. The maximum shear stress tolerance (τmax) correlated well with the cleaning efficiency. Also the change in the electrical resistivity of the spacer fluid after cleaning correlated well with the cleaning efficiency and hence can be used for in-situ monitoring of the cleaning operation.
Sharma, Neha (Woods Hole Group, Inc.) | Storie, Jill (Woods Hole Group, Inc.) | Ivanov, Leonid (Woods Hole Group, Inc.) | Magnell, Bruce (Woods Hole Group, Inc.) | Leber, Michael (Woods Hole Group, Inc.) | Gustafson, Drew (Woods Hole Group, Inc.) | Zimmerle, Heather (Woods Hole Group, Inc.)
The years 2014-2017 marked a period of anomalous and extreme Loop Current (LC) activity that resulted in significant impact on offshore operations for the first 18 months, followed by a 4- to 6-month period of more typical behavior and then 15 months of uncharacteristic inactivity. The objectives of this study are to (i) provide a detailed description of the kinematic structure of the Loop Current Eddies (LCEs) observed during this time frame; (ii) determine the vertical extent of each eddy and the effect of eddy activity on near-bottom currents, and (iii) establish a relationship (if any) between eddy activity and intensity of inertial oscillations within the water column. We present data collected from ADCPs at several locations in the northern Gulf of Mexico along with an extensive network of drifting buoys in correlation with daily frontal analyses and a comparison with historical events. To estimate the intensity of inertial oscillation and its variability in time, we computed rotary current spectra for periods characterized by high and low eddy activity. While circulation patterns during early 2014 were fairly typical, an apparent sudden increase in energy marked the beginning of hyperactivity in late June. Eddies Lazarus, Michael, Nautilus, and Olympus spun off the LC, each eddy experiencing multiple reconnections with the LC before its final separation in addition to amplified intensities (over 3 knots, max 4.5+ knots). December 2015 marked the beginning of the second phase. Another eddy (Poseidon) separated from the LC in April 2016; however, the winding down process of the LC circulation was already in effect. Poseidon did not exhibit a significant northward migration and the LC itself remained far south. In the central Gulf, the passage of Poseidon was followed by the passage of a subsurface cyclonic eddy, without a significant surface expression, propagating westward. For the next 18 months, the LC remained extremely inactive. While currents in the near-bottom layer were not directly correlated with the flows in the upper part of the water column during the period of the high eddy activity, the later period was characterized by more energetic near-bottom flows, suggesting LCE’s may stimulate generation of topographic Rossby waves that cause strong near-bottom intensities. No significant correlation between the presence of LCE’s and intensity of inertial oscillations was found. Results of recent near-surface and water column current observations are presented in the paper.