Ron Deady

Multi-sensor seismic while drilling: field test results

Summary While it may be widely accepted that borehole seismic surveys utilizing a standard surface seismic source can be obtained while drilling there are at least two main issues that need to be well understood in order to make these seismic measurements accurately and reliably: sensor coupling/fidelity, and precision timing. To further complicate matters, the rigors of the drilling environment impose significant constraints on the design and mounting of the seismic sensors and the accuracy of the clock. We have developed a next-generation tool that addresses coupling issues through the deployment of multiple, multiaxis sensors, including ruggedized geophones, seismic accelerometers, and hydrophones, in combination with a novel, highly accurate clock and contingent surface systems. This paper investigates the performance of the new tool design and presents the results of field tests and operations in which seismic data were acquired using multiple sensors and multiple types of sensors in various types of formations, and in deviated boreholes. The data acquired while drilling are compared to baseline commercial wireline VSP measurements in order to verify that the system provides accuracy comparable to that of a standard commercial wireline.

Deepwater hazard avoidance in a large top-hole section using LWD acoustic data

Drilling expensive and challenging wells in deepwater requires significant prewell planning to mitigate risks. Understanding the regional drilling hazards that nearby operators have encountered and correlating them to the current project must be done to gain a clear appreciation of potential problem hole sections. This paper describes a deepwater well drilled by Agip where significant efforts were taken to fully evaluate the potential for a shallow water flow in the top-hole section. Another operator in a nearby block had recently lost well to a shallow water flow. This heightened the concern of the Agip asset team so an extensive pore-pressure analysis of the surface seismic data was undertaken. The results of this analysis indicated that there was also a strong potential for a shallow water flow on this well. In order to build the best possible understanding of the pore pressure profile the surface seismic pressure analysis was taken much deeper than what is customary, in this case to the top of the salt. Prewell pore pressure models confirmed Agips surface seismic pore pressure assessment. As a result, real-time pore pressure monitoring services were deemed essential to closely monitor the progress of the well and, with that information, make real-time adjustments to the drilling parameters (i.e. mud weight) as they became necessary. An extremely important and sometimes overlooked aspect of real-time interactivity is the definition of the role each team member has and how each team member interacts with the others. Assembling a team and defining each members roles and responsibilities in the planning phase streamlines the time-critical decision-making process and allows for a decisive, unambiguous, work flowpath. Figure 1 shows the communication and workflow organization assigned by Agip before the well was drilled. Rig-based personnel are highlighted in green and office-based personnel in blue. The operations geologist was the …