RIASSUNTO
Abstract
In today's drilling environments and economics oil companies demand focus on all aspects of services delivered by the oil field service companies. Safety and efficiency are paramount with cost considerations following closely behind. Reductions of non-productive time are continuously monitored to evaluate service delivery excellence. All economics are impacted by dead or non productive time associated with failed or damaged equipment, logistical complexities, unplanned events (i.e., weather storms), complex reservoirs and drilling trajectories.
A costly yet extremely critical service for the oil companies is the capture of representative fluid samples from the reservoirs they are drilling. This is done today with formation sampling wireline tools (FSWL) lowered into the wellbore days after the drilling of the formation. The timeliness of this information as well as the additional rig costs associated with the capture of this information can be several days or more in additional time for the sampling operation. In many cases, such as in high angled or horizontal wells, the drill pipe is required to convey the wireline to the formations. In these instances the tools cannot be gravity conveyed, which adds cost and additional risk. Because formation sampling while drilling (FSWD) technology has recently been introduced, significant cost savings are possible because the testing and sampling can be performed during the drilling process. It is the objective of this paper to demonstrate an economic model using field examples to evaluate the cost benefit between using FSWL and FSWD fluid sampling operations acquired in deep water fields. Factors considered are the operating costs for FSWL and FSWD, the probability for fishing, reduction in pumping times associated with lower invasion for FSWD and reducing the operational time in high angel wells and the ability to make changes in well construction.
Introduction
When new technology is introduced to the industry, it can be very difficult to evaluate its potential economic benefit. The new technology has the potential to improve the quality and reduce the uncertainties of the information collected, or to obtain similar results at reduced costs. However, the risks and benefits are difficult to quantify. This is particularly true when evaluating similar technologies for wireline (WL) and logging-while-drilling (LWD). With the introduction of FSWD, which offers comparable benefits to FSWL, new methods must be developed to evaluate these technologies and to determine when it is of greater benefit to use the new FSWD rather than the well-established FSWL. This paper introduces a new economic value-added model that uses cost differences and considers the risks involved with its implementation. It is important to first understand the capabilities and potential benefits of FSWD.
Comparing FSWD with FSWL. While FSWD tools have been introduced, many questions still linger regarding the effectiveness of this new technology. Also considering that FSWL tools have been run on drillpipe in ""tool pusher?? mode for decades, these are not true LWD applications. The primary purposes of tool pusher logging have been to deploy FSWL in highly deviated boreholes and to avoid the need to fish a stuck toolstring. The deployment of this wireline tool, however, increases the complexity of a testing job and the amount of rig time required, which directly affects the overall cost.
Innovations in probe designs have been introduced to FSWL, such as the elongated oval-shaped probes for testing in tight laminated sands (Fox et al. 2006).
New focused-sampling probes actually have two flow areas where the inner probe is surrounded by a guard ring that scavenges most of the contamination and maintains lower levels of contamination of the inner probe (Hrametz et al. 1999). These major probe innovations are illustrated in Fig. 1 and must also be considered when evaluating FSWL and FSWD.