Saberhosseini, Seyed Erfan (Islamic Azad University) | Mohammadrezaei, Hossein (Iranian Offshore Oil Company) | Saeidi, Omid (Iranian Offshore Oil Company) | Shafie Zadeh, Nadia (Natural Resources Canada) | Senobar, Ali (Iranian Offshore Oil Company)
Pre-analysis of the geometry of a hydraulically induced fracture, including fracture width, length, and height, plays a crucial role in a successful hydraulic-fracturing (HF) operation. Besides the geometry of the fracture, the injection rate should be optimal for obtaining desired results such as maintaining sufficient aperture for proppant placement, avoiding screenouts or proppant bridging, and also preventing caprock-integrity failure as a result of an extensively uncontrolled fracture in reservoirs. A sophisticated numerical model derived from the cohesive-elements method has been developed and validated using field data to obtain an insight on the optimal fracture geometry and injection rate that can lead to a safe and efficient operation. The HF operation has been conducted in an oil field in the Persian Gulf with the aim of enhanced oil recovery (EOR) from a limestone reservoir with low matrix permeability in a horizontal wellbore. The concept of the cohesive-elements method with pore pressure as an additional degree of freedom has been applied to a 3D fully coupled HF model to estimate fracture geometry, specifically fracture height as a function of the optimal injection rate in a reservoir porous medium. It was observed that by increasing injection rate, all the fracture-geometry parameters steeply increased, but the fracture height must be controlled to be in the reservoir domain and not surpass the caprock and sublayer. For the reservoir under study with the maximum height of 100 m, length of 250 m, width of 100 m, permeability of 2 md, and porosity of 10%, the optimal fracture height is 73.4 m; the average fracture width and half-length are 12.8mm and 55.4 m, respectively. Therefore, the optimal injection rate derived from the fracture height and geometry is in this case 4.5 bbl/min. The computed fracture pressure (49.55 MPa = 7,283.85 psi) has been compared with the field fracture pressure (51.02 MPa = 7,500 psi), and the error obtained for these two values is 2.88%, which showed a very good agreement.
Studies of Alternating Current (AC) interference on pipelines from nearby power lines usually consider the fundamental (50Hz or 60Hz) frequency of the power line currents. However, these currents can also contain considerable harmonics of the fundamental AC frequency. Measurements on pipelines in Canada and Sweden have shown that these harmonics can produce significant interference in the pipe-to-soil potentials. The electromagnetic fields experienced by the pipeline are dependent on three types of parameters. The first is associated with the phase relations of the power line harmonics, classified as ‘positive sequence’, ‘negative sequence’, and ‘zero sequence’. The second is related to the conductivity of the host media (ground) that affects the electromagnetic field experienced by a pipeline. The third is pipeline series impedance and parallel admittance, which introduces additional frequency dependence. This paper examines the frequency dependence of the phase relation of the power line currents, the Earth response, and the pipeline response and shows how they can be combined to provide an AC risk assessment.
Where pipelines share the same right-of-way with the power line, there is considerable electromagnetic coupling between the power line and the pipeline. There has been significant work on this issue1,2, which has been almost exclusively concentrated on 50 or 60 Hz induction in pipelines. However, harmonics have also been observed in pipelines3,4 and this raised concerns about their influence on the safe pipeline operations.
The harmonics produced in a pipeline depend on the amplitude of the harmonic currents in the nearby power line as well as the phase relation between the currents in the different phase conductors. The electric fields produced in the pipeline are dependent on the Earth response and the currents and voltages produced in the pipeline depend on the pipeline characteristics (Figure 1).
This paper examines the frequency dependence of each stage of this process and examines how these combine to determine the harmonic voltages produced on a pipeline.
Baffin Bay, northern Canada, represents the northernmost segment of rifting between Greenland and North America, and can be considered a northern extension of the Labrador Sea extinct rift system between Labrador and Greenland. Many questions remain about the nature of the crust beneath parts of Baffin Bay, although extinct spreading axes and a fracture zone have been previously identified based principally on gravity data. Existing deep seismic coverage over Baffin Bay is spatially limited and mostly concentrated in the north, although two regional 2-D transects span the region from the centre to the southern end of the bay. One of the regional 2-D refraction transects revealed a thick sedimentary package overlying oceanic crust along most of the profile, despite a lack of clear magnetic anomalies within Baffin Bay. To extrapolate the 2-D seismic refraction results offline and resolve the regional crustal structure across Baffin Bay, a constrained 3-D gravity inversion was undertaken. Bathymetry and depth to basement were used to constrain the 3-D inversion and the resolved crustal geometry from existing refraction lines was used to gauge the quality and reliability of the inverted model. The final inverted 3-D crustal structure model for Baffin Bay will provide useful constraints for basin studies and will shed light on its tectonic evolution.
Ikeda, Tatsunori (WPI-I2CNER, Kyushu University) | Tsuji, Takeshi (WPI-I2CNER, Kyushu University) | Takanashi, Mamoru (Japan Oil, Gas Metal National Corp) | Kurosawa, Isao (JOGMEC Technology Research Center) | Nakatsukasa, Masashi (Japan Oil, Gas and Metals National Corp) | White, Donald (Natural Resources Canada) | Worth, Kyle (Petroleum Technology Research Centre) | Roberts, Brian (Geological Survey of Canada)
We performed time-lapse surface-wave analysis to monitor the shallow subsurface at the Aquistore CO2 storage site, managed by the Petroleum Technology Research Centre, Canada. A continuous and controlled seismic source system called the Accurately Controlled Routinely Operated Signal System (ACROSS) is used to enhance the temporal resolution and source repeatability in the monitoring. We extracted hourly-variation of surface-wave phase velocities from continuous seismic data with 4 hour stacking. As a result, we could monitor phase velocities within 1 % accuracy during 1-9 days in the frequency range of 4.5-6 Hz. We identified 2-5 % seasonal variation of phase velocities. The high phase velocities observed in winter can be explained by the degree of freezing of partially saturated rock. Our time-lapse results contributed to improving the accuracy of monitoring deep reflections from the CO2 injection reservoir by correcting seasonal variations of near-surface velocity. The high temporal resolution and accuracy of our monitoring results have the potential to identify sudden changes such as CO2 leakage from CO2 storage sites.
Presentation Date: Tuesday, October 18, 2016
Start Time: 8:00:00 AM
Presentation Type: ORAL
Three measurement campaigns were carried out by Natural Resources Canada CANMET Laboratories over the last thirty years within the Red Lake Gold District, Ontario, to determine the magnitude and orientation of in-situ rock stresses on several levels of the Campbell and Red Lake gold mines, at depths ranging from 600 meters down to 2,000 meters below surface. Stress measurements were carried out using standard CSIR triaxial 'hollow-inclusion' and biaxial 'doorstopper-type' measurement cells. In-situ 3D stress tensors were computed. Increasing with the depth of measurement, the major principal stress varies between 23 and 95 MPa, the intermediate stress, between 14 and 68 MPa, and the minor principal stress, between 4 and 38 MPa. The measured vertical stress component also correlates well with the stress level expected within the Canadian Shield at these depths, ranging from 16 MPa at 580 m below surface up to 54 MPa at a depth of 2,000 m. The average stress ratios measured between the principal and vertical stress components are 1.62, 1.01 and 0.55, respectively, confirming the presence of a strong and consistent shear-stress tensor arrangement for all tensors measured below 650 m. This stress arrangement perfectly fits the geological strain-model proposed by Dubé et al. (2002), to explain the formation and the resulting geometry of the Campbell-Red Lake gold deposit, its evolution over time and the development of high grade mineralization zones at depth. The model was namely validated by the latest stress measurement campaign carried out on the deepest levels of the Red Lake Gold Mine during winter 2011. These measurements are key to understand the influence of such high shear stresses on mine design and excavation stability. Sources of variation, e.g. number and complexity of rock layers, presence of faults and folds, dykes and other major geological features, are discussed. ©Copyright reserved, Natural Resources Canada.
The purpose of this paper is to show early results of surficial geologic mapping of the Arctic Ocean. Analysis of subbottom profiler and multibeam bathymetric data in conjunction with the regional morphology rendered from the IBCAO data are used to map nine surficial geologic units in the Arctic Ocean. For a relatively small ocean basin, the Arctic Ocean reveals a plethora of margin and basin types reflecting both the complex tectonic origins of the basin and its diverse sedimentation history. Broad and narrow shelves were subjected to a complex ice-margin history in the Quaternary, and bear the sediment types and morphological features as a result. Some shelf areas are heavily influenced by rivers. Extensive deep water ridges and plateaus are isolated from coastal input and have a long history of hemipelagic deposition. The flanks of the basins demonstrate complex sedimentation patterns resulting from mass failures and ice-margin outflow. The deep basins of the Arctic Ocean are filled with turbidites resulting from these mass-flows and are interbedded with hemiplegic deposits.
Microbiologically influenced corrosion (MIC) has been considered a significant factor contributing to oil and gas pipeline failures. This type of corrosion results from the activities of microorganisms in the biofilms formed on metal surfaces. The in-situ monitoring of MIC is very challenging as it requires a combination of microbiological, surface analytical and electrochemical methods. Sulfate-reducing bacteria (SRB) are considered a predominant cause of MIC and they reduce sulfate to sulfide through anaerobic respiration. Thus the microbial corrosion can be monitored through the detection of biogenic sulfide resulting from the SRB activities. In this paper, an amperometric sensor was constructed for on-line detection of sulfide. Single-walled carbon nanotubes (SWCNTs) functionalized with a conducting polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) were used to facilitate signal transduction. The SWCNT-PEDOT-PSS modified glassy carbon electrode (GCE) sensor exhibited a large linear detection range, short response time, and high sensitivity for detection of sulfide, through direct oxidation of the sulfide without the assistance of any enzyme and mediator. The results paved the way for the development of on-line biosensors for fast and reliable monitoring of MIC related to SRB activities.
The Rotating Cage is a standardized methodology for investigating the corrosion of metals under flowing conditions. As such, it can be used as a comparative method, for screening inhibitors or identifying the differences in the corrosion-inhibitory properties of different crude oils, as well as simulating flowing pipeline hydrodynamics. It is a complimentary technique to the rotating cylinder electrode and jet impingement method. Whilst it does not permit in situ measurements, it has a distinct advantage over other methods: whilst average corrosion rates are determined through mass loss, the relatively large surface area of the specimens permits statistical analysis of localized corrosion phenomena, monitored through techniques such as laser profilometry.
In this article, we seek to build upon earlier work, both experimental and theoretical, in order to better understand the fluid dynamics of the rotating cage method. Computational fluid dynamics (CFD) simulations were used to conduct a parametric study that investigated the dependence of the wall shear stress as a function of several variables, including: rotational velocity, temperature, fluid viscosity and density, for the standardized rotating cage test equipment. The wall shear stress is commonly used to relate experimental test conditions to flowing pipelines, thus the current study confirms the value of the rotating cage method in simulating pipeline flow.
Sakiyama, N. (Schlumberger) | Fujii, K. (Schlumberger) | Pimenov, V. (Schlumberger) | Parshin, A. (Schlumberger) | Yamamoto, K. (Japan Oil, Gas and Metals National Corp.) | Wright, J.F. (Natural Resources Canada)
Temperature profiles and their transient behaviors obtained using a distributed temperature sensing (DTS) system were measured while monitoring wellbore fluid levels during a methane hydrate production test. The temperature data were obtained in 2008 as part of the JOGMEC/NRCan/Aurora Mallik 2007-2008 Gas Hydrate Production Research Well Program.
Methane hydrate is known to be stabilized under low-temperature and high-pressure conditions. In the Gas Hydrate Production Research Well Program, a depressurization method using an electric submergible pump (ESP) was employed to dissociate the hydrate in the reservoir. For recovering the produced gas and fluid without resynthesizing the hydrate after the dissociation, it was essential that the temperature of the produced fluids flowing up the tubing be controlled.
According to our numerical temperature simulation, the annulus fluid level around the tubing is one of important factors that govern the tubing fluid temperature during the methane hydrate production. If the annulus fluid level is high, the tubing fluid temperature becomes so low that methane hydrate can potentially be formed inside the tubing; thus, understanding fluid levels during methane hydrate production is important for flow assurance as well as bottomhole pressure control. The conventional method for estimating fluid levels in a wellbore employs an acoustic wave reflection technique; however, the accuracy of the survey is subjected to assumption of an acoustic velocity which depends on pressure, temperature, and gas types. On the other hand, estimating fluid levels with a DTS temperature profile is thought to be a more direct method. Although it is not widely known, several papers indicate that the feasibility of estimating fluid levels with the DTS system when the fluid level is static.
In this paper, we demonstrate the feasibility of estimating dynamic fluid levels using a DTS system. The dynamic trend in estimated fluid levels with the DTS system shows qualitatively good agreement to that estimated with the pressure on the completion assembly and the pressure at the casinghead. The difference in fluid levels between the DTS temperature-based and the pressure-based methods quantitatively explains a void fraction in the two-phase flow of the fluid and the gas. The analysis presented in this paper is based on field data collected during methane hydrate production, but it is potentially applicable to any conventional production scheme that employs artificial lift.
A Telluric Current Simulator for Pipelines D.H. Boteler, L. Trichtchenko, C. Blais, R. Pirjola Geomagnetic Laboratory Natural Resources Canada 2617 Anderson Road Ottawa, Ontario K1A 0E7 ABSTRACT Telluric currents due to geomagnetic field variations have long been known to cause variations in pipe-to-soil potentials (PSP) on pipelines. These are incr easingly being taken into account in the design of cathodic protection systems for new pipelines. Online services are available for modelling telluric currents but cannot handle all pipeline configurations . This paper describes the development of a new telluric simulator, based on a more versatile modeling technique that can include more details of a pipeline such as branches and ot her features. This can show the pipe-to-soil poten tials produced by specified telluric electric fields. De scriptions are also provided for features of the telluric simulator that allow modeling of the pipeline response using elec tric fields calculated for past geomagnetic disturbances.