A New Well Positioning Technique: Access-Independent Ranging Solution for Providing Accurate Well Completion

摘要

Magnetic ranging has been used in heavy oil drilling environments, primarily in steam-assisted gravity drainage (SAGD) applications, to eliminate accumulated directional survey errors. SAGD applications require drilling several pairs of horizontal, parallel wells separated by a few meters. More than 2,000 well pairs have been drilled using a ranging technique in which a device generating a magnetic field is deployed in one of the SAGD wells, and a device to measure the magnetic field is deployed in the adjacent SAGD well. This ranging technique has succeeded in accurately controlling the desired separations and directions relatively between the well pairs. However, the cost for access to both wellbores of the well pair has created a high demand for new ranging techniques that require access to only drilling wellbore. This paper presents a new well positioning method that provides innovative magnetic ranging without access to the wellbore of a target well through the use of surface excitation. The surface excitation is connected to the wellhead of the target well to transmit a current signal along the cased-hole target well; the array gradiometer in the nearby drilling well receives the corresponding magnetic fields and calculates the relative distance and direction between the two wells. The active magnetic, wellbore access-independent, magnetic ranging system provides several advantages over currently available systems, including reduced cost and risk to the operator, improved equipment logistics, elimination of the wireline ranging tool deployment, and reduced personnel to deliver the service, relative to current commercial systems. Various laboratory tests and field trials based on a discovery tool were conducted exclusively in SAGD wells to validate the proposed concept and to demonstrate the capabilities of providing reliable and accurate ranging data for relative well positioning and well placement applications. The results show excellent agreement on ranging distance and direction measurements between the discovery tool and the industry standard tool. The described logging while drilling (LWD) technique presents an alternative ranging method to existing wireline techniques in SAGD applications. It is also applicable in wellbore intersection and well positioning applications without a target wellbore access.