Drilling wells in complex geological structures from offshore platforms, or onshore in areas with land access restrictions often creates complex S-shaped wells. In many such wells, high-angle doglegs cause problems with wireline key-seating, thus restricting reservoir access. When Logging While Drilling (LWD) data acquisition is not an option and Pipe-Conveyed Logging (PCL) is discarded because of its risky and time-consuming nature, many wells could end up without critical Formation evaluation data. To overcome reservoir access challenges in the Sirikit Field in Thailand, a Through-Drill pipe Logging (TDL) technique has recently been introduced to complete formation evaluation. This method safely and effectively overcomes the complex well trajectories and associated wireline conveyance problems, such as key-seating. Slim 2.25" OD logging tools including Triple Combo (TC), Quad Combo (QC) and formation pressure tester and fluid sampler are deployed on wireline through open-ended drill pipe into open-hole without difficulties and with full well control maintained at all times. A standard TDL operating procedure has been developed between wireline and drilling crews, allowing for safe and fast operations. The driller is able to have well control, with pipe being reciprocated regularly. Typically the drill pipe is run with a reamer shoe to allow borehole cleanout operations in the same run. The TDL deployement method is now a key component in the standard decision tree for data acquisition strategy in Sirikit Field and it has been successfully introduced in the Sirikit Field in May 2016. Since then, a total of 59 runs have been performed in 31 wells where wireline reservoir access problems were encountered, saving an estimated 1,240 hours of combined rig time not counting any potential wireline fishing jobs that would likely have occurred. A near 100% success rate is maintained, measured by reaching well TD and acquiring all desired wireline data. Petro physicist and geologists are no longer left without the crucial formation evaluation data they require for successful reservoir management. This paper present a case study that clearly demonstrates that the TDL deployment technique can be very effective in providing safe and efficient wireline access to reservoir sections in S-shaped wells with risky wellbore conditions, where high-angle doglegs and key-seating would otherwise have restricted the ability to obtain Formation evaluation log data and fluid samples.

Exploration and development wells are increasingly drilled to deeper depths and lower porosities, in hotter formations. These conditions increase the challenges for Formation Tester's (FT's) to acquire accurate formation pressures in a timely and cost efficient manner. One of the most important constraints on current FT acquisition is the downhole formation temperature. The Pattani and North Malay basins in the Gulf of Thailand (GoT) are known to be one of the highest temperature locations where FT data is routinely acquired. Successful exploitation of the hydrocarbon resources in these basins is strongly driven by cost efficiency and the characterization of the many individual sands that are part of the complex fluvial stratigraphic framework. Reservoir pressure, fluid type, inflow performance and sand-to-sand correlation are some of the objectives for acquiring FT data and are used to manage the many wells drilled each year in these basins. Chevron (Thailand) E&P and PTTEP are the main operators in the GoT, drilling roughly 450 wells each year and over 80% of the wells have bottomhole temperatures in excess of 320 degF. Roughly 80% of the wells drilled require FT logging in the data acquisition program. The main challenge in this high temperature environment for formation testing acquisition is that pressure gauges need to be stabilized to eliminate a transient effect due to high temperature, in order to obtain an accurate pressure measurement. This can lead to longer logging times with the current tools available and lost efficiencies, particularly for wells with many individual hydrocarbon bearing sands (high pay counts).To improve efficiency and the actual formation pressure management, a proposal was made to develop a High Temperature FT tool in early 2009. This paper discusses the development challenges for FT's in this high temperature area, including gauge selection, gauge limitation, gauge temperature transient effects and logging procedures. After an intensive working period, a specially-made flask to cover certain parts of the tool for heat transfer and mitigation was introduced. Since then, this new FT service has been deployed in more than 20 wells in the Gulf of Thailand. This paper also presents the actual field data from the new tool in terms of data quality and accuracy compared to previous generations of FT, and the resultant efficiency gains from rig time savings. With this development, it is currently possible to obtain accurate formation pressure data, even in the extreme high temperatures found in the GoT, where satisfactory results were not possible in the past.

The Sirikit field is a mature reservoir located in the Phitsanulok Basin in north-central Thailand. The field produced first oil in late 1981. Typical logging programs include a complete set of openhole (OH) logging suites such as a triple combo, including gamma ray-neutron-density-resistivity, or quad combo including gamma ray-neutron-density-sonic-resistivity. The reservoir production and injection are carried out with commingled completion. Therefore, wireline formation testing, and sampling tools are usually included for acquisition. Development wells with highly deviated trajectories pose challenges to conventional wireline logging (WL) operations, especially in deep wells exceeding 3,000m. In sections with high dogleg severity, the tools are prone to sticking, and the cable can become key-seated due to hole conditions, deviation, washouts or caving. Log data is a vital component for studying geological complexity, completion and production planning. Therefore, there is a need for an alternative method to convey WL tools to reach the bottom of the hole. In 2015, an alternative conveyance method called "through drillpipe logging" (TDL) was proposed to mitigate the risk of WL tools sticking or hanging up in an openhole environment. This method uses a slim-chassis, 2.25 in. outer diameter (OD), WL logging suite that enables the tool to be run through the drillpipe. The first TDL job was trialed in Thailand in May, 2016 as the second run after the WL run hung up. This TDL run hosted a full triple-combo suite and WL formation testing tools, which reached total depth (TD) while overcoming hole-condition issues that had been experienced during the first run. Following this successful log run, the TDL has become the preferred contingency planning option to support WL operations in challenging wells. To date, a total of 64 jobs, including triple combo (TC), quad combo (QC), formation testing & sampling (FTS) and cross-dipole sonic (CDS) have been executed successfully with less operating time than conventional contingency processes involving wiper trips, tool pushing, or pipe conveyed logging. This track record confirms that TDL provides a fit-for-purpose solution for logging in challenging conditions.