Exploration for heavy oil, in an offshore setting carries special challenges and risks, especially during the well testing phase. Bringing the heavy oil to surface and then disposing of this oil efficiently without polluting the offshore environment is a challenge. Flow testing oil with APIs as low as 8 degrees would be challenging in itself; when this oil is also sour, the challenges are magnified many-fold, especially when considering the limited space on offshore drilling rigs. Saudi Aramco has started a program aimed at exploration and evaluation of heavy oil reserves in the Arabian Gulf. The objective of testing this sour, heavy oil was to obtain reservoir fluid samples, get productivity data and characterize the reservoir. While attempting to dispose of the oil in an efficient manner, initial attempts to test this heavy oil were unsuccessful. Prematurely terminating these tests resulted in not obtaining all of the required test data. A heavy oil team was formed in early 2008 to determine solutions to the inability to properly characterize the reservoir on heavy oil well tests. This multidisciplinary team of professionals held two workshops, where heavy oil experts from major service companies provided their global expertise. This information was then blended with local operational requirements to create a unique well testing design. This design has successfully been implemented in two wells (onshore and offshore). The use of an Electric Submersible Pump (ESP) although common in production scenarios, was successfully implemented for the first time on a heavy oil drill stem test in Saudi Arabia. This paper summarizes the problems associated with testing heavy oil, the options studied, the reasons for selection of the chosen test method, the downsides of the selected plan, the trial testing on land and the successful implementation of the final plan in an offshore environment. It is a summary of the planning process necessary to get a good heavy oil test in a sensitive offshore environment.

The abrasive Pre-Khuff sandstones combined with high downhole temperatures and the propensity for BHA and bit sticking present a uniquely hostile drilling environment. These limit run durations and the ability to optimize ROP with the use of conventional rotary assemblies, PDMs/conventional turbodrills and/or rotary steerable systems. Catastrophic damage or loss of drill strings, poor hole quality and logging problems are common even with the advancements in PDC bit technologies. Of the systems listed above, historically, turbodrilling systems have best addressed the high temperatures and the abrasive nature of the Pre-Khuff formations and held the potential for drilling economics optimization but have been unsuccessful in addressing bit sticking challenges. The resultant development of best practices produced only marginal results because they require surface intervention and thus did not fully address sticking problems (in particular bit sticking). The engineering challenge was to develop a downhole device that automatically engages and imparts sufficient drill string torque to maintain bit rotation. The turbodrill device disengages when conditions return to normal and returns the operation to high productivity drilling without surface intervention. The turbodrill device coupled with advancements in BHA design, stabilizer and jar placement along with formation characterization and drill bit technology, is the solution to bit sticking incidents. Presented with this advancement in turbodrilling technology, the Operator/Service Company team has completed trials using this technology and presents data that supports the use and benefits of anti-sticking technologies. With this success, the team has regained focus on drilling optimization and reset the goal for single run-casing point to casing point. Introduction Saudi Aramco continually seeks ways to improve drilling efficiencies through the difficult Pre-Khuff Formations. This paper is about a fortuitous trial of last resort that has delivered favorable results. In Saudi Arabia, Pre-Khuff Formations (Unayzah, Jauf; Tawil, Sharawra, Qusaiba, Sarah, Qasim; and Saq) are encountered at depths between 13,000 and 17,000 feet. These strata primarily comprise sandstones interbedded with shales, limestone, dolomite, anhydrite and siltstones. Sandstones with some siltstone predominate in the top Unayzah strata downward through the Qusaiba. At the bottom, the Sarah can also include some interbedded shale. The Unayzah and Jauf are generally characterized by hard, abrasive sandstones interbedded with shale and siltstone. Unconfined compressive strengths can reach 40,000 psi with internal angles of friction ranging from 25° to 75°. Hardness, abrasiveness, toughness, irregularity in size and orientation of rock constituents, and problems with sticking all contribute to a significant challenge and expense associated with drilling in the Pre-Khuff Formations. High wear rates on bits and BHA components cause a significant potential for premature equipment failures, limit on bottom rotating time, and necessitate long and frequent trips. The Upper Pre-Khuff (Unayzah to Jauf) strata are the most difficult of the Pre-Khuff formations to drill. These strata typically consist of very irregular, fine to coarse grained pebbles and conglomerates that can vary significantly in their dimensions and hardnesses (both in adjacent wells and at different depths in a particular well) and the Jauf formation may also contain Pyrite.