Success from Subsea Riserless Well Interventions

Abstract

Abstract This paper describes how Statoil, over a period of 10 years, have qualified and implemented Subsea Riserless Light Well Intervention (RLWI) applications as their primary means of intervening in subsea wells. The paper will also demonstrate the value of RLWI in relation to the company's Increased Oil Recovery (IOR) goals. Subsea wells represent the area where least well intervention work has been done, and where the biggest practical and technical challenges also lie. Hence less oil is recovered from subsea completed fields than from those with fixed platforms. RLWI is a cost effective intervention method that allows an operator of subsea wells to increase production and optimize utilization of vessels and rigs. Statoil is a leading exponent of RLWI services, utilizing two specialized and modern vessels on full year contract. A third vessel is currently being considered. The total RLWI activity for 2010 was 671 days, spanning a total of 32 different jobs. This paper will describe the development of these applications from 2000 until today covering a total of 125 individual operations. Statoil has 34 subsea fields, of which 32 are on the Norwegian continental shelf with a total of around 460 individual wells. Light Well intervention has been performed on 11 of these fields. Experience so far indicates that there are no limitations on equipment regarding interface to subsea templates. In this paper the contract philosophy for these services will also be discussed. Further on, the agreement between the different production assets for sharing of resources will also be described. The technical achievements and limitations will be listed and described. Then the needs of the future will be described and prioritized. Finally, the economic benefit and contribution of introducing Riserless Light Well Intervention will also be highlighted. The following three conclusions on RLWI will be elaborated on in this paper: Improves HSE in subsea well interventionsImproves recoveryIntervention cost is cut by more than half compared with anchored rigs and riser systems