Wireline Replacement in Pilot Wells by LWD Tools Including Formation Testers

Abstract

The use of an eight-inch diameter formation-tester-while-drilling tool for 12 ¼ into 16-in. holes has provided the option to significantly if not totally replace wireline logging operations in pilot sections of planned horizontal wells in Brazil. When using LWD tools only, sections of a pilot interval do not need to be plugged and abandoned, as had been the practice. The option with a complete suite of LWD tools can greatly reduce operational risks and save time and money. Savings of up to six rig days and US$ 900.000,00 can be expected. In the past, a 12 ¼ in pilot section was drilled before the horizontal section of a planned horizontal well was developed. The purposes of the pilot section were to confirm top and base of target reservoir and evaluate its production characteristics. While drilling pilot sections, the LWD tools were limited to gamma, resistivity and pressure while drilling. Thereafter, a more comprehensive wireline logging suite was run including, wireline-run formation testers. To avoid the need for a costly pipe-conveyed logging runs, these sections were also limited to inclinations less that 50 degrees. After the logging runs, the pilot sections were typically plugged and abandoned with a sidetrack section drilled off the top of the last cement plug. The availability today of LWD formation tester allows for a new and less costly option. The 12 ¼ in. section of the planned well takes an S-shape profile, getting close to the target reservoir at inclination higher than called for in running wireline, dropping off to reach the base of the reservoir and continuing to its final TD destination. It is not necessary to plug and abandon all the pilot section, and the planned drilling, including logging, can be completed more quickly and efficiently. Introduction With the introduction of the 8 inches GeoTap (Sperry's formation tester while drilling tool for 12 ¼ to 16 inch holes), the wireline logging operation in the pilot wells can be restricted or even totally replaced. A long section of the pilot can be kept for the subsequent horizontal well, greatly reducing operational risks. Time and cost savings up to 6 rig-days and US$ 900.000,00 can be expected. In this paper, we will evaluate the savings in development wells where it is possible to use the LWD tool set replacing conventional wireline logging, when drilling 12 ¼ inches pilot well. To help understanding the proposal either from the point of view of the well construction engineers, the reservoir engineers and the geologists (which are normally involved in the planning and execution of the job), some basic concepts on drilling, logging and logging-while-drilling were inserted in the paper.