Space weather effects on drilling accuracy in the North Sea

The oil industry uses geomagnetic field information to aid directional drilling operations when drilling for oil and gas offshore. These operations involve continuous monitoring of the azimuth and inclination of the well path to ensure the target is reached and, for safety reasons, to avoid collisions with existing wells. Although the most accurate method of achieving this is through a gyroscopic survey, this can be time consuming and expensive. An alternative method is a magnetic survey, where measurements while drilling (MWD) are made along the well by magnetometers housed in a tool within the drill string. These MWD magnetic surveys require estimates of the Earth’s magnetic field at the drilling location to correct the downhole magnetometer readings. The most accurate corrections are obtained if all sources of the Earth’s magnetic field are considered. Estimates of the main field generated in the core and the local crustal field can be obtained using mathematical models derived from suitable data sets. In order to quantify the external field, an analysis of UK observatory data from 1983 to 2004 has been carried out. By accounting for the external field, the directional error associated with estimated field values at a mid-latitude oil well (55 N) in the North Sea is shown to be reduced by the order of 20%. This improvement varies with latitude, local time, season and phase of the geomagnetic activity cycle. By accounting for all sources of the field, using a technique called Interpolation In-Field Referencing (IIFR), directional drillers have access to data from a “virtual” magnetic observatory at the drill site. This leads to an error reduction in positional accuracy that is close to matching that of the gyroscopic survey method and provides a valuable independent technique for quality control purposes

Applications of aerospace technology to petroleum extraction and reservoir engineering

Through contacts with the petroleum industry, the petroleum service industry, universities and government agencies, important petroleum extraction problems were identified. For each problem, areas of aerospace technology that might aid in its solution were also identified, where possible. Some of the problems were selected for further consideration. Work on these problems led to the formulation of specific concepts as candidate for development. Each concept is addressed to the solution of specific extraction problems and makes use of specific areas of aerospace technology

Novel annular flow electromagnetic measurement system for drilling engineering

Downhole micro-flux control drilling technology can effectively solve drilling accidents, such as kick and loss in narrow density window drilling scenarios. Using a downhole annular flow measurement system to obtain real-time information of downhole annular flow is the core and foundation of downhole micro-flux control drilling technology. The research work of electromagnetic flowmeters in recent years creates a challenge for downhole annular flow measurement. This paper proposes a new method for an annular flow measurement system based on the electromagnetic induction principle. First, the annular flow measuring principle, the weight function, the density of virtual current, and the magnetic field of the annular flow electromagnetic measurement system are described. Second, the basic design of the annular flow electromagnetic measurement system is described. Third, model simulation and dynamic experiments on an annular flow electromagnetic measurement system are carried out. The simulation and experimental results show a linear relationship between the system output and the annular flow rate, and also verify the correctness of annular flow electromagnetic measurement theory

Mathematical Model and Simulation of a Pneumatic Apparatus for In-Drilling Alignment of an Inertial Navigation Unit during Horizontal Well Drilling

Conventional methods in horizontal drilling processes incorporate magnetic surveying techniques for determining the position and orientation of the bottom-hole assembly (BHA). Such means result in an increased weight of the drilling assembly, higher cost due to the use of non-magnetic collars necessary for the shielding of the magnetometers, and significant errors in the position of the drilling bit. A fiber-optic gyroscope (FOG) based inertial navigation system (INS) has been proposed as an alternative to magnetometer -based downhole surveying. The utilizing of a tactical-grade FOG based surveying system in the harsh downhole environment has been shown to be theoretically feasible, yielding a significant BHA position error reduction (less than 100m over a 2-h experiment). To limit the growing errors of the INS, an in-drilling alignment (IDA) method for the INS has been proposed. This article aims at describing a simple, pneumatics-based design of the IDA apparatus and its implementation downhole. A mathematical model of the setup is developed and tested with Bloodshed Dev-C++. The simulations demonstrate a simple, low cost and feasible IDA apparatus

Measuring the Magnetic Content of Drilling Fluid

Magnetic contamination of drilling fluid can impact the accuracy of the directional surveying by shielding the magnetic field. Additionally, this contamination, such as swarf or finer magnetic particles, can agglomerate on the downhole tool or BOP and cause tool failure in the worst-case scenario. Thus, making the measurement of the magnetic content of the drilling fluid necessary. However, there is no recommended practice in API or ISO for this purpose. A simple experimental setup and measurement system was developed that can be easily deployed in the rig site to measure the magnetic contamination of drilling fluid. 47 drilling fluid samples were collected from a multilateral production well drilled with a semi-submersible drilling rig located in one of the North sea’s fields. The magnetic content of these samples was measured using the established method, and the microstructure of the collected content was analyzed using a Scanning electron microscope (SEM) and X-Ray Diffraction Analysis (XRD). Ditch magnets are commonly installed in the flowline on the rig to remove the swarf and finer magnetic particles if their design is optimized. Ditch magnet measurement data of the well that the drilling fluid samples were collected from is presented. Operational details and common factors that might build up the production of the magnetic content were also investigated. By comparing the measured magnetic contamination of the drilling fluid samples and ditch magnet measurement data, it was possible to evaluate the efficiency of the ditch magnet system

DOWNHOLE RF COMMUNICATION: CHARACTERIZATION AND MODELING OF WAVEGUIDE PROPAGATION IN A FLUID-FILLED DRILL PIPE

Current technologies for downhole communication in oil and gas drilling applications are severely limited in data rate and latency. This work proposes that a system based upon guided wave propagation could be designed to utilize a wireless, radio frequency (RF) signal to yield tens of megabits per second of data transfer. To determine the feasibility of the proposed system, a test setup was built to measure attenuation of RF signals transmitted through a pipe filled with various drilling fluids. A finite element analysis model was also built to further investigate waveguide propagation of electromagnetic signals in a fluid filled pipe. The measurement setup was validated using fluids of known dielectric properties. A number of a drilling base fluids and oil-based fluids were measured and their dielectric properties calculated. The feasibility of the proposed communication system is not promising for liquid based fluids. However, there is significant potential in an air-based system

Application of Fiber Optic Technology in Reservoir Monitoring

The purpose of this thesis was to gain an overview of fields of application of fiber optic technology in reservoir monitoring, how such a measurement system is operated, and challenges that can occur. For automated and integrated processes in the exploration and production of hydrocarbons, the information available before, during, and after operations is of great value. Where to place wells and templates, at which rate and when production and injection is to take place are just a few of the decisions in such processes. Fiber optic technology which is common in reservoir monitoring tools in a production well, is also used for seismic and monitoring of the subsurface and pipelines along the seabed. Fiber optic measurement systems are of great value thanks to real-time data, which are an advantage in decisions to be made on short notice. By implementing fiber optic sensing elements along a wellbore, from the reservoir section and up to the surface, well intervention operations, testing of downhole safety equipment, well integrity assurance, and an active reservoir management on drainage and injection strategies can be optimized and profitability maximized. With in-well fiber optics already in place, they can be used for various operations. From cementing a liner, reservoir monitoring, and fluid characterization, to measuring strain and conditions of downhole equipment. Published papers, course material and equipment from Weatherford, discussion with field specialists, and personal experience have been the basis of the thesis. It was successfully demonstrated how a bad splice affects the optical power transmitted through a fiber optic cable, that attenuation on the emitted light has a boundary, and how important a test of an entire measurement system before operations is. The installations by Equinor at the Johan Sverdrup field are a good example of benefiting from implementation of technology from the start of development. The digitalization of the green field is part of their high ambition of a 70 % recovery. Fiber optics are a great choice of measurement systems for reservoir monitoring with many sensing elements already available in today’s market, and will most likely be a preferred choice for monitoring many wells and reservoirs in the years to come

Development and evaluation of a coaxial cable sensing system for CO₂ sequestration wellbore integrity monitoring

Downhole monitoring plays a crucial part in geological carbon dioxide (2) sequestration. Various downhole monitoring technologies have been explored and applied, but they are either expensive or have system longevity issues. To address this issue, a robust and cost-effective downhole sensing system based on distributed coaxial cable sensors is developed and evaluated in laboratory, and a numerical simulation with staged finite element model is conducted to study the feasibility of using the coaxial cable sensing system for monitoring and evaluation of wellbore stability during CO2 injection. The real-time distributed sensing system is composed of Fabry-Perot interferometer based coaxial cable temperature and strain sensors. A high pressure high temperature (HPHT) sensor testing system is developed to study the temperature sensor accuracy, sensitivity, stability, hysteresis, and crosstalk effect under simulated downhole conditions. A lab-scale prototype of the casing imager based on strain sensors is developed and tested in laboratory to prove its real-time monitoring ability in casing axial compression, radial expansion, bending, and ovalization. A parametric study with staged finite element analysis is conducted to study the feasibility of using the casing imager in wellbore stability monitoring and evaluation during CO2 injection in the Weyburn field. The system is proved to perform under 1,000 psiaand 110 ⁰C, with real-time monitoring ability in casing axial compression, radial expansion, bending, and ovalization. And the parametric study with finite element model not only proved the feasibility of using the system for wellbore stability monitoring and evaluation during CO2 injection in the Weyburn field, but also provided insight into the best cementing practice and injection conditions as guidance to avoid leakage risks in a geologic CO2 sequestration project --Abstract, page i