Eltsov, T. (Ali I. Al-Naimi Petroleum Engineering Research Center, King Abdullah University of Science and Technology) | Patzek, T. W. (Ali I. Al-Naimi Petroleum Engineering Research Center, King Abdullah University of Science and Technology)
Electrically resistive composite casing materials are being introduced to the oil & gas industry. Resistive casing enables electromagnetic logging for exploration and reservoir monitoring, but it requires development of new logging methods. Here we present a technique for the detection of integrity of magnetic cement behind resistive casing. We demonstrate that an optimized induction logging tool can detect small changes in the magnetic permeability of cement through a non-conductive casing in a vertical (or horizontal) well. We can determine both integrity and solidification state of the cement filling annulus behind casing. Changes in magnetic permeability influence mostly the real part of the vertical component of magnetic field. The signal amplitude is more sensitive to a change of magnetic properties of the cement, rather than the signal phase. Our simulations show that optimum separation between the transmitter and receiver coils ranges from 0.25 to 0.6 meters, and the most suitable magnetic field frequencies vary from 0.1 to 10 kHz. A high-frequency induction probe operating at 200 MHz can measure the degree of solidification of cement. The proposed method can detect borehole cracks filled with cement, incomplete lift of cement, casing eccentricity and other borehole in homogeneities.
The objective of this work is to present the development of a numerical model for wave propagation in materials with time-varying, heterogeneous, and non-linear properties. Materials change with time as the result of complex linear and non-linear processes, which can occur due to natural causes or induced. Wave phenomena in this context brings about an interesting and complex problem, which involves the solution to coupled equations which describe interlinked multiphysics phenomena. Thus, understanding the dynamics of this interaction is beneficial to numerous applications across different industries and applied research; e.g. acoustic characterization of moving fluids, laser-fluid interaction, distributed optical fiber sensing, photonic integrated systems, among others. Numerical models, therefore, are indispensable to gain a deeper insight about the physical dynamics of the process and, ultimately, purvey a platform to design and test new applications and technologies.
Over time some numerical models have been proposed to simulate wave phenomena in these situations. The method and solution reviewed in this work provides a unique solution to develop and optimize multiple applications. For example, it can be used to model the interaction of electromagnetic waves with travelling Bragg mirrors produced by temperature or pressure changes in optical fibers, which is the basis of fiber-based distributed fiber sensing; the scattering of acoustic waves by transient disturbances in fluid flow that may arise from gas bubbles or variations in the density of fluids; and the propagation of an electromagnetic pulse in a rapidly moving and varying fluid.
The mathematical description of the process was derived originally for electromagnetics; yet, the numerical solver and mathematical treatment is generic and can be applied to other wave phenomena. The derivation departs from physical principles to write a generalized set of equations that describe wave propagation in time-varying, heterogeneous, and non-linear materials. The resulting set of hyperbolic partial differential equations (PDE) includes diffusive and convective terms that fully describe the wave interaction and process. Linear and nonlinear spatial and time heterogeneities in the material are assimilated into the convective terms of the hyperbolic wave equation. The solver was implemented using a semi-discrete and multidimensional scheme based in the finite-volume method which is highly scalable. Extension to other wave phenomena is discussed by analyzing the parameter correspondence for the acoustic and electromagnetic case.
Mitkus, Alexander (Helmerich & Payne Technologies) | Maus, Stefan (Helmerich & Payne Technologies) | Willerth, Marc (Helmerich & Payne Technologies) | Reetz, Andrew (Helmerich & Payne Technologies) | Oskarsen, Ray Tommy (Add Energy) | Emilsen, Morten Haug (Add Energy) | Gergerechi, Amir (Petroleumstilsynet)
As development of the Barents Sea continues with new plays such as the Castberg, accurate specification of the local magnetic field is important to reliably infer the orientation of the bottomhole assembly (BHA) in horizontal drilling. Since magnetic fields at high latitudes vary spatially and temporally, one requires both spatial models and a way to capture temporal changes. Large temporal changes in the magnetic field can severly distort measured azimuths and therefore must be corrected for. This study, based on a report written for Petroleumstilsynet (Maus et al., 2017), shows that in regions of the Barents Sea within 50 km of a magnetic observatory, either the nearest observatory, interpolated infield referencing (IIFR), or the disturbance function (DF) method may be used for corrections in wellbore surveying to meet accuracy requirements. IIFR and DF will give better error reduction but are slightly more complicated to implement. At distances between 50 km and 250 km, the disturbance field (DF) method best meets accuracy requirements. In remote regions beyond 250 km, a local observatory must be deployed to meet the highest accuracy specifications, but the DF will still far outperform the other interpolated methods at such large distances from an existing observatory. Despite having focused on the Barents Sea region, this comparison of the accuracy of different spatial and temporal magnetic field mitigation methods for wellbore surveying is applicable to high latitude northern and southern regions across the globe.
Directional surveys are taken while drilling a well to enable well placement and to avoid hitting other wells. This requirement is becoming increasingly important as reservoirs become more complex to reach and fields become ever more crowded. Taking directional surveys either before, during or post connection takes time, waiting for surveys to be pumped up takes longer and may need to be repeated if a critical survey cannot be taken first time which is a particular problem in shallow hole offshore operations. This paper outlines an industry first technology that will effectively eliminate surveying time, a definitive continuous survey will be available to the directional driller at all times, eliminating the need to take and wait for a survey before making the next directional drilling decision.
Continuous 6 axis surveys are cutting edge replacement for the static six axis Measurement While Drilling (MWD) surveys which have been used as the primary surveying tool worldwide for decades. The three magnetometers and Inclinometers provide an accurate inclination and azimuth when the drillstring is stationary. Continuous six axis MWD surveying could be described as a static survey captured continuously while drilling a stand allowing for accurate inclination and azimuth at all times. The directional driller will know where they are definitively at all time, eliminating the requirement for surveying time, enabling efficient decision making while eliminating the need for additional pump cycles, their associated wash outs and the directional difficulties that stem from that.
Field test examples of this continuous 6 axis MWD surveying will be shown with comparisons between other MWD systems these will be analyzed to establish consistency and accuracy. An error model for the continuous six axis survey will be discussed in some detail, as it is inherently different to a normal static MWD survey and comparison will be made to other error models. The time savings involved with continuous six axis surveys will also be shown, with a discussion on the associated benefits to the directional driller from reduced pump cycles.
Directional surveying is generally seen as a must have on a rig, however the associated rig time is considerable. This unique and world first method will discuss how continuous six axis survey are made, the accuracy modelled and so how the industry can eliminate rig time associated with MWD surveying.
Positional uncertainty is a critical component of managing collision risk while drilling. Ensuring that survey data meet the requirements of their uncertainty models has historically required complicated analysis. Most consumers of survey data are not experts and knowing when escalation is required in a high-risk situation can be unclear. This problem will increase as more data is evaluated by automated decision-making systems. Two novel methods are proposed to analyze sets of survey data against uncertainty models with the intent to answer the questions: "Is it safe to continue drilling" and "Does this wellbore need to be resurveyed?".
The proposed methods evaluate a survey set using the error sources, error magnitudes, and error propagations contained in positional uncertainty models. A quality control error covariance matrix is constructed, and the set is evaluated against it. Two statistical outputs are generated: a statistical distance that explains how well an additional survey fits with the existing survey data, and an overall survey assessment that describes the likelihood of an error-model compliant system producing the observed dataset.
The methods are used to evaluate downhole magnetic survey data that was flagged after evaluation by subject matter experts, but traditional quality control measures had failed to identify as problematic. Errors that do not fit the expectations of the error model are flagged in a way that is apparent to a non-expert user and can be integrated into an automated alert system. How to include these procedures in drilling workflows is discussed, including when escalation to a subject matter expert is required.
A system is proposed where, with minor modification to existing error models, this analysis can be automated for wellbore surveys of all kinds. Additional discussion is included on how these methods will fit into the upcoming API recommended practice on wellbore surveying.
The use of advanced solid-state gyroscopic sensors has now become both a viable and practical option for high accuracy wellbore placement, with the potential to out-perform traditional mechanical gyroscopic systems. This paper describes how the contributions of the new gyroscope technology are causing service providers to reconsider current survey practices, and to examine how the new gyroscopic survey tools can be best used for wellbore surveying and real-time wellbore placement.
The simultaneous application of multiple survey tools, largely made possible as a result of the unique attributes of solid-state gyroscopic sensors (including small size and significant power reduction), has clear benefits in terms of enhanced well placement, reliability and the detection of gross errors in the survey process. Further benefits accrue through the combination of different, but complimentary survey methods. This paper focuses mainly on the benefits of combining gyroscopic and magnetic measurements to reduce or remove the known errors related to the Earth's magnetic field to which magnetic survey systems are susceptible; errors in total magnetic field, declination and dip angle.
In this context, the use of statistical estimation techniques based on performance models of the survey systems used is described. For post-drilling surveys (using drop survey tools or wireline-conveyed tools for example), post-run analysis of the data using least-squares estimation techniques is appropriate. Alternative methods capable of achieving real-time data correction during drilling are also described and results are presented to demonstrate the potential for enhanced magnetic survey performance.
The principles described may be used when running basic magnetic measurement while drilling (MWD) systems, and for systems that employ field correction methods, such as the various in-field referencing (IFR) techniques, that are frequently used. The proposed methodology is of particular benefit in the former case, allowing enhanced magnetic surveying to be achieved without the need for expensive and complex magnetic field correction procedures. The potential also exists either to identify or to correct possible errors in the IFR data when such methods are used. This information may be of great value for the safe drilling of additional wells in the same region.
A Sand Wash Basin well was drilled for an unconventional target for which the measured core properties did not match production for the well. The crushed-rock porosity for the core suggested a bulk-volume hydrocarbon (BVH) of 1.5 to 2.0 p.u., indicating that the stimulation would have to be draining at approximately 400 ft vertically. To resolve this incongruity for further field development, we investigated the validity of crushed-rock porosity and nuclear magnetic resonance (NMR) to accurately assess the resource. Initial results using conventional 2-MHz core NMR yielded results similar to those for crushed-rock porosity. Because unconventional rocks have very fast relaxations in NMR, it was then theorized that with the use of a high-resolution 20-MHz machine, the signal/noise ratio would improve and create a more-accurate quantification of porosity components. The results of using a high-resolution 20-MHz NMR showed a porosity increase from 6.5 p.u. using the Gas Research Institute (GRI) methodology (Luffel et al. 1992) to 14 p.u. on an as-received sample, creating a large increase for in-place calculations. As a result, a process termed sequential fluid characterization (SFC) was developed using high-resolution 20-MHz NMR to quantify all components of porosity (i.e., movable fluid, capillary-bound water, clay-bound water, heavy hydrocarbon, residual hydrocarbon, and free water). This method represents an alternative to crushed-rock methodologies (such as GRI and tight rock analysis) that will accurately quantify movable porosity as well as the other components without the errors introduced by cleaning and crushing. After investigating the application of SFC with the high-resolution 20-MHz NMR, it was identified that other unconventional plays (such as Marcellus and Fayetteville) have an average of 45% uplift on in-place calculations using SFC-based movable porosity. Identifying in-place volumes correctly can vastly improve the characterization of fields and prospects for unconventional-resource development, and, as is shown in this paper, SFC can be used to do so with a great effect on volume assessment in unconventional reservoirs.
In this paper we provide an overview comparing induction motors (IMs) and permanent-magnet motors (PMMs) for electrical-submersible-pump (ESP) applications. The design and performance differences of the two types of motors are compared and discussed. The PMM advantage and unique applications are highlighted. The requirement of a different control strategy to operate a PMM is described. Some key safety aspects that field engineers need to be aware of with PMMs are also addressed in this paper.
The information we present includes a literature review and the latest research and development results. We cover the operating principles of the IM and the PMM, selection of permanent-magnet materials, operating frequency, stator windings, and magnetic poles. PMMs offer better efficiency, higher power-factor performance, and compactness. Ideal applications include slim-well applications, through-tubing rigless deployment, Y-tool completion, and electric-submersible-progressive cavity pumps (ESPCPs). We will also shed some light on why conventional IMs cannot be used to drive ESPCPs directly without speed-reduction gearboxes.
It is very likely that the use of PMMs will increase for ESP applications in the near future, and this will require engineers to acquire a basic understanding of this technology. This paper intends to provide a high-level comparison between IMs and PMMs in the ESP industry.
Chen, Xun (Drilling and Production Technology Research Institute of Liaohe Oilfield) | Sun, Shouguo (Drilling and Production Technology Research Institute of Liaohe Oilfield) | Tong, Deshui (Drilling and Production Technology Research Institute of Liaohe Oilfield)
The trajectory control quality is the key technology when using SAGD dual horizontal wells to produce heavy/super heavy oil. The systematic study of trajectory control, CT scanning diagnosis and completion decision has been carried out to guarantee the forming and keeping of steam chamber and enhance the drainage continuity and well-bore life so as to realize economical and effective development. In order to realize precise control of the trajectory of dual horizontal wells, the method with space rectangular target for dual horizontal wells and MGT magnetic-steering technology as its core, has been developed. The CT scanning diagnosis system of SAGD trajectory based on the medical technique has been developed to realize real-time scanning and predicting of the horizontal intervals of the paired horizontal wells. The timely warning and guidance of trajectory adjustment are available when the deviation of the relative position of the two wells from the space rectangular target occurs. After drilling, the space position relation of arbitrary cross-section along the trajectory axis is analyzed through the scanning diagnosis system, and scientific evaluation of the SAGD production is conducted using the SAGD efficiency coefficient method. If the relative position of certain intervals of the two wells is pretty near and there will be the risk of steam breakthrough, physical isolation of the intervals are recommended with casing and thermal packers. The technology has been applied in 12 well-groups in the Liaohe Oilfield, most of the dual horizontal wells have kept favorable position relations. During the injection well of Du-A well-group, due to the large formation dip, the scanning diagnosis system sent out warning signals when 2/3 of the horizontal interval had been drilled, then technicians adjusted the trajectory timely. After drilling, it was found that the distance between the two wells was less than 4m for a 4-meter interval at the 2/3 of the horizontal interval. During the design of completion strings, a blind tube is used to replace the screen in the interval. Two thermally-setting packers are designed respectively for the upper and lower end of the blind tube to realize physical isolation so as to ensure the formation of the steam chamber in the later period and guarantee favorable oil drainage. The overall production of the block has been increased by 15% compared to the wells in the earlier stage. After study, the SAGD trajectory control and completion decision technology with integral constraints of the space rectangular target, real time control of CT scanning diagnosis system and decision guidance after completion has been developed to successfully remove the potential developing troubles caused by trajectory control quality. With favorable applications in the field, the technology has become an important method to guarantee SAGD development effects.
Condition monitoring and defect inspection in the buried oil and gas pipelines, made of ferrous material, has always been a challenge for all organizations operating in the Oil & Gas sector. Pipelines can be inspected in two ways, internally and externally. Internal inspection by ILI tools require special infrastructures like pig launchers and receivers along with pre-preparation before inspection like internal cleaning there is the data collecting and analysis process which is time-consuming. Whereas in communally used external inspection a group of workers drive a vehicle along the pipelines to perform visual inspection of the pipelines for detection of leakage or any other kind of visible damages. Such manual external inspection is highly inefficient, expensive and hazardous. In such a way it is difficult to obtain any important information for the anomalies brewing in the buried pipes or cathodic protection layer.
A lot of work has been done towards developing NDT technologies to inspect pipelines. However, most of the NDT sensors work only in close vicinity of the pipeline surface which requires an excavation of the pipelines and exposing the structure. This shortcoming of NDT techniques has attracted researchers towards other NDT techniques such as non-invasive magnetomatric diagnosis (NIMD) which allows non-contact detection of anomalies from distance in the core metal of the pipelines deeply buried underground. NIMD sensors work on principle of measuring distortions of residual magnetic fields conditions by the variation of the pipeline's metal magnetic permeability in stress concentration zone due to combined influence of various factors such as residual stress, vibration, bending and loading of pipelines, installation stress and temperature fluctuations etc. These handheld magnetic sensors are used manually by field operators therefore inspection of long pipelines in extreme environmental conditions is not feasible. A non-contact external robotic inspection system, Autonomous Ground Vehicle (AGV), carrying such non-contact magnetic and visual sensors is designed and tested in this work.
AGV is equipped with two kinds of sensors, the first navigation sensors and the second inspection sensors. Accurate autonomous tracking of the pipelines by the AGV is achieved by fusion of three navigation mechanisms based on visual data, GPS and pipe locator. The pipe locator in combination of CP post is one of the most extensively used sensors in the oil and gas industry for tracking the buried pipelines. In this work manually used pipe locator is now fully automatized for autonomous tracking of the buried pipelines by the AGV. For this purpose, a hybrid automata trajectory controller is developed for a non-holonomic AGV where a PID controller is combined with non-linear forward velocity of the AGV depending on the lateral distance error and angular alignment error. Field experiments are conducted successfully to demonstrate accuracy of the newly designed controller. Successful development of such complex mechanism requires solution of many critical challenges like teleoperation, system and supervisory controls, trajectory tracking, image processing and sensor data fusion.