To ensure the highest level of accuracy in wellbore placement, the integration of many survey management techniques is required, which in certain situations includes the integration of relative wellbore position measurements (ranging). The goal is to identify and eliminate all errors and biases that are internal and external to the survey tool to help reduce the positional uncertainty of the wellbore and to determine the relative position of the current wellbore to surrounding wells.
Designing a workflow to achieve the necessary combination of analyses to cover all potential situations required the development of an application that allows an expert user to select and configure the appropriate corrections. It had to be easy to use and provide empirical solutions to the wellsite users in a timely manner to help limit rig interruptions and associated nonproductive time (NPT). Rigorous workflow analysis is required to ensure a high level of quality for the final surveys to meet industry expectations for well positioning and also criteria from governing bodies that demand the final well position be formally recorded.
Current practice involves multiple steps for survey correction, beginning with basic quality assurance and increasing in complexity by identifying instrument biases in accelerometer and magnetometer readings, compensating for local magnetic and gravity anomalies in the subsurface, identifying interference generated by ferromagnetic materials in the drillstring itself and surrounding wells, and compensating for diurnal fluctuations in the earth's magnetic field caused by changes in the intensity of solar radiation. Each of these corrections involves different data sources, from the raw responses of the measurement devices to time-based magnetic observatory data, and the cumulative effect of all of these factors should be determined as accurately as possible to help minimize uncertainty.
The workflow seamlessly combines all of the different correction methodologies currently available and allows the automation of the calculations after they have been configured by the expert. Multiple wells can be assessed concurrently, increasing the amount of time the expert spends on analysis and interpretation and reducing the time required to obtain and manipulate data.
This workflow is unique to the industry because it combines every survey correction methodology available, enabling the analysis of all potential environments and resulting in greater accuracy. Accurate determination of the wellbore position should significantly reduce health, safety, and environment (HSE) risks associated with the potential for wellbore collisions caused by the inherent uncertainty of the wellbore location and can significantly improve reservoir production through optimum placement.