Marlim Field: The Evolution of Deepwater Drilling/Completion/Workover

Abstract

Abstract Marlim Field is located in the northeastern portion of Campos Basin, offshore Brazil, in water depths ranging from 600 m(1,968 ft) to 1,100 m (3,608 ft). The field was discovered in September 1984 by the wildcat 1-RJS-219 A, in 853 m (2,800 ft) water depth. The areal extent of Marlim Field is 152 Km2(52 mi2). The main objective of this paper is to give a general outlook of the drilling, completion and workover operations in Marlim Field. It reviews well design development, drilling progress and the associated costs from the field earlier appraisal wells till the most recent development wells drilled in the area. The paper also describes the evolution of completion with emphasis in the work done in improving well design, minimizing problems and optimizing operations. The main causes of intervention are listed and described. Finally, the future plan for Marlim Field that includes the utilization of technologies such as extended reach, slender and multilateral wells is also depicted. Introduction Since the drilling of the wildcat well 1-RJS-219A in 1984, many developments related to drilling technique were obtained in Marlim Field. Improvements in well design, drill bits, drilling fluids and the use of new technologies helped to increase well safety, cut cost and raise oil production. The evolution of Completion on Marlim Field occurred basically on subsea tree installation systems and its connections to flowlines, methods of sand control, horizontal well completion and reservoir pressure monitoring with permanent downhole gauge. Installation of subsea tree and its connections has undergone three different techniques. It started with the Lay Away method, passed by the Vertical Connection method and nowadays it is being done with the Direct Vertical Connection method. Like in most very deepwater field, Marlim unconsolidated sandstone reservoir is a sand producer. Due to its peculiar characteristics, tools, procedures and technologies were customized to achieve good performance on sand control in vertical, directional and horizontal wells. To obtain regular pressure and temperature data from subsea wells with wire line gauges from a completion rig is economically unfeasible. The alternative is the permanent downhole gauge (PDG). At first the mean time before failure (MTBF) of the PDG systems installed in Marlim was very low. After changes on management and equipment the performance of this system improved a lot. The goal is to equalize the MTBF of PDG to the mean time before workover. Drilling Well Design and Operational Procedures - In the earlier stage of the drilling in Marlin, when few data were available, one of the main causes of preoccupation was related to the shallow and unconsolidated sediments. Initial designs used the common practice of jetting 48 or 46" pipes. The difficulty of handling and controlling the passage of these heavy pipes through the rotary table soon made the engineers look for other options. In 1992, the designers substituted the 46" pipes for a 42" housing and conductor pipe of 13 meters length resulting in reduction of time and consequently cost. In 1993, the designers decided to jet a 30" casing having a floating shoe at the end. This procedure not only proved to be better and more acceptable solution, but also reduced remarkably the time of the first phase as shown in Fig. 1.