Measurement-while-drilling (MWD) surveying is one of the important prerequisites for the successful delivery of directional wells because the survey defines the accurate wellbore position and orientation of the bottomhole assembly (BHA) in real time during the drilling operation. There were many modifications performed in MWD measurements evolution progress over the years, but none of them resulted in achieving the six-axis surveying measurements that obtained in dynamic conditions with at least the same accuracy as static surveys. Realizing the true potentials of taking the survey measurements in the rotating mode helped to optimize drilling operations and minimize the risks associated with stationary survey methods. The definitive dynamic survey (DDS) can be accurately performed while drilling in both rotary and slide modes. The DDS eliminated survey-related rig time, i.e., working the drillstring to release the torque, providing zero motion while making and sending downhole survey measurements, or spending additional time to resurvey the interval for various reasons.

A major directional oilfield services provider pioneered a new MWD surveying technology that implemented in the projects in the Caspian Sea. The technology delivered definitive surveys while on-bottom drilling with full parameters and complete data quality control. Several operational runs have been recently conducted with the aim of comparing and qualifying DDS to industry standard gyro and MWD surveys. The MWD DDS survey was conducted in complex 3D well profiles, including a curve section and tangent at near vertical and high angle through a continuous turn interval. The results showed an excellent match both in inclination and in azimuth. Based on the results of evaluating the technology in this location, DDS surveys enhanced rig operations efficiency, improved trajectory control, and provided higher survey density than that from traditional stationary MWD surveys.

This paper presents the recent results obtained from implementing the DDS technology while drilling in the Caspian Sea region and reveal the best practices for planning and performing other similar jobs. The paper includes the procedures required to take definitive non-static surveys, ensuring the DDS data are sent continuously to the surface and meet survey acceptance criteria in terms of sensor misalignments, shock and vibration parameters, eddy current compensation, and phase shift corrections. To validate these continuous survey measurements, a field test survey comparison was performed between a conventional static survey and a gyroscopic survey. In addition to a conclusion, the paper will present the recommendations for the well construction efficiency optimization while drilling through a depleted reservoir.

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