A variety of magnetic ranging methods are used to determine distance and direction between a magnetic field sensor and a magnetic field source. If the sensor is in a near vertical hole, it may be difficult to orient the sensor's axes relative to known world coordinates, since no gravity high side is available. This can create difficulties calculating and applying ranging results. A magnetic azimuthal toolface may also be impaired due to magnetic interference. To address this problem, we combine and align ranging and gyro systems in one tool-string and use simultaneous gyro attitude measurements to define the orientation of a ranging system with respect to True North. We apply this technique to two distinct magnetic ranging methods. The first method consists of a solenoid based ranging system. The example shows how this method was used to drill a precisely parallel wellbore in a close proximity to a previously drilled vertical well. The second described method consists of an at-bit-while-drilling ranging system that was used to safely pass by a vertical well while drilling a horizontal well in a close proximity. The paper compares the results of alternative north orientation techniques for magnetic ranging versus the simultaneous gyro attitude referencing. The alternative techniques include a magnetic north orientation and the north orientation derived from a prior downhole survey and gravity high side tool face. The results show that the described technique can improve magnetic ranging accuracy by up to 10-fold over the previous methods. The paper provides 2D and 3D visualization and numerical analysis of the listed north orientation techniques applied to the magnetic ranging methods. Simultaneous gyro measurements can significantly improve magnetic ranging accuracy. The applications for the described technique include relief well drilling, plug and abandonment, collision avoidance/risk mitigation, civil and mining projects.

The development of heavy oil assets in Canada, and worldwide, often relies on Steam Assisted Gravity Drainage (SAGD). Directional drilling and surveying these horizontal wellbores presents a host of challenges to the service provider and operator alike. One such challenge relates to conventional surveying techniques and the cumulative errors associated with this approach. Once integrated over the length of the horizontal wellbore, downhole positional uncertainty can typically be 30 m or more in lateral uncertainty, and 5 m or more in vertical uncertainty. These errors present a number of complications in the development of the asset. To address the issue of cumulative uncertainty in horizontal wellbores, a method of absolute referencing to a surface generated magnetic signal has been developed and successfully deployed in the field. The surface installation is engineered to provide a precise location based on the measurable magnetic field for any point in a desired wellbore placement region. The surface installation consists of conductors arranged on surface above the intended well path, and the exact location of the installation is determined by way of a differential Global Positioning System (GPS) unit. While drilling, the installation is energized, and the Measurement While Drilling (MWD) tool samples the superimposed magnetic field vector. These results are transmitted to surface via standard real time telemetry, and a North, East and True Vertical Depth (TVD) position of the sensor is calculated via surface software in real time. The absolute positioning technique has been deployed on eight SAGD drilling wells at subsurface depths of 100 to 250 m, for two different operators in Northern Alberta, with encouraging results. On six of the eight wells, the calculated position of the sensor agreed with the integrated position as determined through standard MWD surveying. However, on two of the eight test wells, the absolute ranging determined position disagreed from the MWD integrated position by 10 m or more. The discrepancy observed could be accounted for by systematic errors in MWD surveying. Here we report in detail on a three well redrill program from this set. For shallow horizontal wellbores, the accuracy of the method described can be far superior to surveying techniques such as MWD or gyro at the end of the horizontal section, with estimated uncertainties that can be an order of magnitude smaller than the accumulated uncertainty associated with conventional methods. With non-cumulative uncertainty, the absolute positioning method can be used to complement SAGD drilling operations in a number of ways. Some potential uses of the technique include: no-access active wellbore twinning, vertical observation well avoidance, infill drilling, and TVD confirmation. Through these applications, it is predicted that operational costs at the rig site will be drastically reduced (via the elimination of wireline, tractor units and survey management techniques) and reservoir drainage will be better optimized by the deployment of the system.

Summary The growing problem of well-to-well fracture interactions in North American shale plays dictates the need for more accurate interlateral spacing measurements. Conventional wellbore surveying techniques, such as magnetic and gyroscopic measurements while drilling (MWD), cannot guarantee optimal placement due to growing systematic errors that dominate survey uncertainty. This uncertainty may impede optimal field stimulation modeling because the wellbore positioning data used in the analytical calculations are inaccurate. Multiple industry technical papers demonstrate a correlation between interlateral spacing and the severity of frac hits. The interlateral distance measurements are used in the calculations for optimal reservoir stimulation and frac hit modeling. With present commodity prices, the industry cannot afford suboptimal field development caused by inaccurate well placement. In this paper, we compare the conventional survey technique with a commercially proven long-distance active magnetic ranging system that supplements the traditional MWD system. We apply relevant survey error models to two exemplary well pads—an actual well pad from a West Texas shale play and a realistic, although hypothetical, example—and compare them with relative ranging uncertainty. The first example shows that MWD positional error exceeds relative ranging uncertainty while the wells are still near vertical at approximately 6,500 ft measured depth (MD). The second example shows that interlateral spacing uncertainty using active magnetic ranging can be 50% of the MWD semimajor error at the end of the curve at 10,000 ft MD [8,910 ft true vertical depth (TVD)] before the lateral section starts. The MWD uncertainty then gets larger due to systematic survey errors multiplied in the “dead reckoning” computation process. With the magnetic ranging applied while drilling, the ranging uncertainty stays practically the same throughout the whole well, enabling tenfold improvement in interlateral spacing accuracy.

This paper describes how active and passive magnetic ranging logging used while drilling subsurface intervention wells shows characteristics of the target well casing integrity and damage. Over the course of the development of a novel active magnetic ranging system and through several years of commercial application, data has been collected and analyzed to understand the characteristics of casing damage. This paper explains the methods used in field operations to collect this data. Using the gathered information, various stages of casing damage and poor integrity are shown. Results obtained from active and passive magnetic ranging are presented in the context of identifying casing damage. This is a departure from the standard methods of interpreting the data as it is not focused on locating a wellbore but determining the integrity of the casing. Casing integrity in idle wells is usually understood by conventional logging techniques until there is a restriction or damage on the well. Magnetic ranging logging performed during the intervention to abandon these wells can give an indication to operators of the casing integrity that otherwise would have been unknown without access to the damaged well. This can help optimize subsequent abandonment procedures as well as assist with field planning into the future to mitigate issues stemming from casing integrity and to identify the causes of previously unknown critical casing damage. The paper reports surface experimental data and compares it with two field examples. In the first field example, the passive magnetic interference from a hundred-year-old casing in the offset well caused more than 100000nT deviation from the reference field approximately 1ft away from the offset well, suggesting severe casing damage. The active magnetic signature measured simultaneously approaches zero, pointing to a lack of electrical continuity in the offset casing caused by a complete break. The second field example shows an offset well segment with passive interference of 7000nT in the presence of a stable active magnetic signal at approximately 2ft separation between wells due to possible casing damage without complete separation. The passive interference increases to 14000 nT at deeper depth while the active signal approaches zero due to a complete casing break. Novel application using the data collected by active and passive magnetic ranging techniques is being applied for the understanding of issues related to casing integrity.

The field experience in the continental US suggests that approximately 33% of plug and abandonment operations are non-routine, and 5% require re-entry (Greer C.R., 2018). In some scenarios, the most cost-efficient option for the intervention is drilling an intercept well to re-enter the target well or multiple wells externally using advanced survey management and magnetic ranging techniques. This paper presents the methods applied of relief well methodologies from the planning to execution of a complex multiple-well abandonment project. Improvements in Active Magnetic Ranging sensor design and applications have improved the availability of highly precise tools for the purpose of locating and intercepting wellbores where access is not possible. These instruments were commonplace on relief well interventions, however, have found a new application in solving one of the major issues facing the oil and gas industry. Subsurface abandonments are a complex task that requires a robust methodology. In this paper, we describe the techniques that have been built upon the best practices from industry experience (ISCWSA WISC eBook). This paper also illustrates how the combination of advanced survey management, gyro surveying, and magnetic ranging can be used following the best industry practices for fast and cost-efficient non-routine plug and abandonment. Case studies of several abandonment projects are presented showing the various technical challenges which are common on idle and legacy wells. The projects include wells that are currently under the ownership of an operator and orphaned wells that have been insufficiently abandoned and left idle over many decades. The case studies outline how the application of relief well methodologies to the execution of complex sub surface interventions led to the successful outcomes of meeting environmental and government regulations for wellbore abandonment. This includes performing multiple zonal isolations between reservoirs, water zones and preventing oil and gas seepage to the surface. The projects and their outcomes prove economically viable strategies for tackling the growing issue of idle and orphaned wells globally in a fiscally responsible manner. Combining industry best practice methods for relief well drilling, along with the technological advancements in magnetic ranging systems is a solution for one of the largest dilemmas facing the oil and gas industry in relation to idle and orphaned wellbores. These applications allow previously considered impossible abandonments to be completed with a high probability of long-term success in permanent abandonment.