Patent ID: 8708053
Filing Date: 2014-04-29
Classification: E21B

Abstract:
1. A method for installing a riser to extend between a FPU (floating production unit) and a well head lying at the sea floor, by connecting lengths of pipe sections in series while holding them primarily vertically at a side of said FPU and lowering the pipe sections into the sea, to create a pipe string which has a near end at said FPU and an opposite far end which is repeatedly lengthened, and when the far end of the pipe string portion lies in the vicinity of one of said well heads lowering said far end and connecting it to the well head, wherein said step of lengthening includes coupling said far end of said pipe string to a tug line on a tug boat and operating said tug boat to pull said far end forwardly away from said FPU while said pipe string portion extends from said FPU to said tug line of said tug boat, wherein: said step of lengthening includes initially positioning the tug boat at a tug position (A) close to the PDU and extending a long enough length of said tug line from a winch on said tug boat to the far end of the pipe string while said pipe string includes at least one pipe section, so the tug line extends from the tug boat in a double catenary curve to the pipe string, and operating said winch to pull the tug pull line to shorten it until the tug line extends in a single catenary curve from the far end of the pipe string to the tug boat and the pipe string extends in a double catenary curve; repeatedly moving the tug boat to positions (B, C) progressively further away from said FPU, to move the pipe string far end closer to the well head.