Geomagnetic referencing uses the Earth’s magnetic field to determine accurate wellbore positioning essential for success in today’s complex drilling programs, either as an alternative or a complement to north-seeking gyroscopic referencing. However, fluctuations in the geomagnetic field, especially at high latitudes, make the application of geomagnetic referencing in those areas more challenging. Precise crustal mapping and the monitoring of real-time variations by nearby magnetic observatories is crucial to achieving the required geomagnetic referencing accuracy. The Deadhorse Magnetic Observatory (DED), located at Prudhoe Bay, Alaska, has already played a vital role in the success of several commercial ventures in the area, providing essential, accurate, real-time data to the oilfield drilling industry. Geomagnetic referencing is enhanced with real-time data from DED and other observatories, and has been successfully used for accurate wellbore positioning. The availability of real-time geomagnetic measurements leads to significant cost and time savings in wellbore surveying, improving accuracy and alleviating the need for more expensive surveying techniques. The correct implementation of geomagnetic referencing is particularly critical as we approach the increased activity associated with the upcoming maximum of the 11-year solar cycle. The DED observatory further provides an important service to scientific communities engaged in studies of ionospheric, magnetospheric and space weather phenomena.
A significant contribution that some oilfield services companies provide for drilling operators today is directional well planning. A major task in the process is to identify and analyze the risk of wellbore collisions. If there is a risk of collision beyond acceptable limits, risk management must be applied. The first part of this process is to collect data. The second step is to analyze the potential risk. The risk not only involves a financial aspect but also HSE (Health Safety and Environmental), so it is imperative that we make the right decision using the most effective tools. Failure to take the right precautions may result in potentially catastrophic human and environmental implications. Generally this is already a complicated task. It gets particularly complicated when this is done at high latitudes and in certain wellbore orientations. Much of the industry today still believes that wellbores are represented accurately by surveys. While in the majority of cases this is somewhat true, the uncertainty and probabilistic nature of the measurement is often overlooked or misunderstood. Few people in the industry today actually understand how this translates to anti-collision also known as collision avoidance. Even fewer understand how much effect your latitude can have on this type of calculation. This paper will address these complications. After a short overview on wellbore placement, the paper will first discuss some theory on what makes high latitude wellbore placement challenging and when is it a relevant consideration. How it relates to collision avoidance will be explained. The current gaps in the industry today will be revealed and options to close those gaps are discussed. Upcoming technologies for reducing risk are reviewed. The second part of the paper will focus on risk management; namely mitigation and prevention. Case studies will be reviewed. Common misconceptions will be eliminated. The paper will attempt to set a foundation of understanding of the fundamental important considerations for anyone involved in collision avoidance in high latitude locations such as the Arctic.
The eni Petroleum Nikaitchuq field is located offshore in the Beaufort Sea within the North Slope region of Northern Alaska. The 12-1/4" intermediate section of the Nikaitchuq wells are drilled with a Rotary Steerable System (RSS) at high inclination prior to landing near-horizontal in the reservoir. The intermediate hole section passes through a very abrasive sand with an unconfined compressive strength (UCS) of approximately 22 ksi called the Lower Ugnu.Historically, the drilling of the 12-1/4" intermediate section has been drilled with two to three bit runs consisting of various polycrystalline diamond compact (PDC) and tri-cone designs. This was due to the abrasive nature of the Lower Ugnu combined with interbedded soft sand causing ledging, high stick-slip and lateral vibrations which lead to consequential bit/BHA damage and a reduction in drilling efficiency.With the objectives of drilling the section in one run and to minimize damages to the RSS and MWD, a vibration mitigation workshop was conducted between the Nikaitchuq drilling team and key service company experts. The workshop team focused on four strategies to mitigate vibrational issues:1. Bottom Hole Assembly modification.2. Introducing new technologies and tools into the drill string to capture high density data and mitigate vibration.3. Mapping and prediction of the hard streaks within the intermediate section.4. Modification of drilling practices where possible.BHA and bit vibration modeling, new vibration mitigation tools, Measurement While Drilling (MWD) and multi-axis downhole vibration measurement data, BHA and stabilizer reconfiguration, as well as implementing various drilling parameters were all investigated and applied in both the front end and at the rig site. This paper demonstrates the systematic approach the Nikaitchuq drilling team implemented to mitigate damage to the bit and downhole tools as well as improve drilling performance by minimizing stick-slip and lateral vibrations.
Scope of this paper is to describe the acid stimulation campaigns carried out in Ghana Offshore field between 2019 and 2020. The campaigns were carried out with a Light Well Intervention (LWI) vessel using different subsea equipment which allowed to safely perform the stimulation operation connecting the vessel to the X-tree production facility.
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