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.

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.

Determining reservoir pressure and confirming fluid type in development wells is of major interest to many reservoir engineers. Because of the high costs and operational risks of having a wireline formation tester (FT) stuck downhole, operators seek reliable technologies that not only deliver the information they need but also mitigate the chances of losing the tool downhole. A new generation of slim, light-weight FT technologies can help make production-management decisions, especially in the often complex geometry of development wells. The Sirikit field Onshore Thailand is an extensively faulted and heterogeneous reservoir, therefore continuously updated pressure profiles have become the key in refining reservoir models. Productive zones are typically thin, but highly permeable. Traditional open hole (OH) log evaluation is insufficient to distinguish fluid types and formation fluid identification (FID) is required in every zone before completion. Because wireline FTs often have thick bodies which are pressed against the borehole wall and sampling takes at least one hour of pump out, they present an increased risk of getting stuck. A smaller diameter FT was evaluated whose body equally centralized in the well during a test in order to dramatically reduce the risk of differential sticking. However it was not clear whether the new tool could similarly distinguish between hydrocarbons and water in a synthetic based mud (SBM) environment using capacitance and resistivity sensors. Four wells with various trajectories and fluid types were selected to benchmark the new tool. Both traditional and new slim FTs were run in the hole (RIH), monitored in real time and the capabilities of the two tools were cross-checked against each other. The results showed that both tools required a similar pump out volume to reach a clean sample. Despite the oil-base mud environment, the slim tool was able to distinguish the transition from mud filtrate to formation hydrocarbons, and in wells where water-base drilling fluids were used, formation water could be similarly recognized. All water samples were directly drained at surface to verify the in-situ real time measurements and oil samples were sent to the lab. The results showed a remarkable consistency in most cases and during trial tests the slimmest sampling tool exhibited a tremendous value in the first stage of field development and it is continuously used nowadays in newly drilled wells. A slim testing and sampling tool shows good reliability for basic fluid identification and is especially suitable for wells with differential sticking issues. Globally, this tool may provide a solution of future wireline pressure and sampling, which can help operators to make proper reservoir-management decisions, especially in complex geometry wells or challenging geological formations.