Technology Advancements in Optimum Wellbore Placement

Abstract

Advances in drilling technology are now making possible the drilling and completion of oil and gas wells that just a few years ago would have been inconceivable. Significant advances in downhole tool sensor placement and reliability are aiding operators in optimizing wellbore placement to within a matter of tens of centimetres in the vertical plane. Over and above this lateral well placement in the 3D horizontal plane now make it possible to intersect high permeabily horizons and steer the wellpath in three dimensions to ensure the well is able to maintain its position within the "sweetest zone". In this paper the authors will demonstrate how advanced technology was used to drill the Sotong 5, 6 and 7 trilateral wells using a rotary closed loop drilling system. These types of tools provide enhanced drilling-while-steering efficiency and improved hole quality. It comprises a surface to downhole guidance system, formation evaluation (with optional LWD) and downhole pressure monitoring. These tools can automatically guide the bit to a preprogrammed target and two-way surface communication allows rigsite engineers to adjust the well trajectory to meet drilling objectives and redirect the wellpath based on real-time formation logs, through the utilisation of reservoir navigation services (geosteering). This eliminates the "wait and see" aspect of drilling with conventional steerable systems, which often results in less than optimal well placement, as well as getting continuously updated models of the placement of the drainhole within the reservoir. This technology is augmented through realtime wellsite information transfer from the rigsite to the office. Therefore the critical well path decisions can be made in real time by the team in the office and implemented at the wellsite instantaneously. The paper will discuss tangible performance metrics and attempt to quantify through statistical analysis the added value of such systems. Introduction The Sotong field is located in Block PM-12 in the southern part of the Malay basin, offshore Peninsular Malaysia. The field, being marginal, was selected to be developed utilizing multilateral technology. An initial economic study indicate that using conventional deviated wells would not be cost effective. The development drilling commenced in July 1998, and Rotary Steerable System was deployed one year later, in June 1999, which was the first application of the system in Malaysia. Futhermore, geosteering technology was utilized to precisely locate the optimum wellbore placement in the target reservoir. Advancement in information technology provides a real-time communication and data transfer between the offshore installation and Petronas Carigali HQ. Technical Objectives The objective was to efficiently drain a marginal reserve using multilateral Level 4 technology. The well paths were precisely placed in an optimal position using rotary steerable systems and geosteering in order to ensure optimum production and field life.