Heave Compensated Managed Pressure Drilling: Lab Experiments

Abstract

The world energy demand is ever increasing with every year. Oil and gas make up approximately 55% of energy sources to meet the demand. However, hydrocarbons reserves are limited and according to peak oil theory, the peak oil has already reached/surpassed. Hence, it is a vital challenge to meet the demand by innovative and technically advance solutions to add to existing reserves. One of the main solutions is to drill more wells in the fields and environments that were deemed to be undrillable originally. Managed Pressure Drilling is a technique that allows to drill wells in very difficult scenarios such as narrow pressure window, depleted fields, extreme loss circulations etc. The hydrocarbon production from Norwegian Continental Shelf is on a decline. Hence it is even more incentive to add to the existing reserves as even 1% increase could be equivalent to 300 billion NOK. North Sea is considered as one of the harsh environments to drill wells in. This is mainly because low temperatures and large waves. Large waves induce large heave which results in large surge and swab pressures when drill-pipe is in slips for making connections. This project deals with concept of keeping the bottom-hole pressure to almost constant value for Managed Pressure Drilling in such scenario. A lab scaled model is prepared during the previous work for this project. The model consists of bottom-hole assembly, copper tubing representing a well, choke system and pump. The work presented in this report describes various experiments conducted to determine the control valve characteristic for the choke system. This is done so that the established characteristics can be integrated to set up the fully automated system. The report also contains the description of the work done for various experiments for copper tubing. A series of experiments was performed to establish and verify the pressure drop equation for the copper tubing. This can be implemented in the model to calculate the pressure drop for any given flow rate in the copper tubing. The choke characteristics and pressure drop equation were established successfully to be integrated in model and ultimately achieve the goal of maintaining almost constant bottom-hole pressure.