RESERVOIR MONITORING THROUGH MODIFIED CASING JOINT

摘要

An apparatus and a method for controlling oilfield production to improve efficiency includes a remote sensing unit that is placed within a subsurface formation, an antenna structure for communicating with the remote sensing unit, a casing joint having nonconductive "windows" for allowing a internally located antenna to communicate with the remote sensing unit, and a system for obtaining subsurface formation data an d for producing the formation data to a central location for subsequent analysis. The remote sensing unit is placed sufficiently far from the wellbore to reduce or eliminate effects tha t the wellbore might have on formation data samples taken by the remote sensing unit. The remote sensing unit is an active device with the capability of responding to control comman ds by determining certain subsurface formation characteristics such as pressure or temperature, and transmitting corresponding data values to a wellbore tool. Some embodiments of the remote sensing unit include a battery within its power supply. Other embodiments include a capacitor for storing charge. In order for a communication link to be established with the remote sensing unit through a wireline tool in a cased well, a casing joint includes at least one electromagnetic window that is formed of a non-conductive material that will allow electromagnetic signals to pass through it. In the preferred embodiment, the electromagnetic windows are formed to substantially circumscribe the casing joint to render it largely rotationally invariant. The electromagnetic windows are formed of any rigid and durable non-conductive material including, by way of example, either ceramics or fiberglass.