Special Report - Pressurized Coring Equipment

Pressure Core Equipment used by the
 Gulf of Mexico Gas Hydrate JIP Drilling Program

Pressure Core Equipment - Photo Gallery

One of the key objectives of the ChevronTexaco Gulf of Mexico hydrates Joint Industry Project is the collection and analyses of deepwater sediment samples. Because these samples may contain hydrate which is only stable at specific temperature and pressure conditions it is necessary to use specialized sampling equipment. Otherwise, the combination of reduced pressure and increased temperatures as the sample is retrieved through 4,000 feet of gulf seawater will fully dissociate the hydrate, leaving only gas and water. Although techniques exist to infer hydrates presence from distinctive geochemical markers, we have lost the ability to image the nature of hydrate distribution, or to conduct measurements of the various physical and chemical properties of hydrates in the host sediments.

There are three types of coring equipment being used on the Uncle John. The Fugro Hydraulic Piston Corer (FHPC) is a standard coring system that retrieves samples without preserving pressure or temperature. The Fugro Pressure Corer (FPC) and the HYACE Rotary Corer (HRC) are two wireline-conveyed (lowered and retrieved through the drillpipe on wires) devices that are designed to collect approximately 1 meter of sediment sample and preserve it in pressurized autoclaves. In both cases, the cores are brought to the surface as quickly as possible, and placed in an ice bath where the sample chamber is extracted from the device and transferred to shipboard labs for analysis. However, the two devices have several distinct differences.

Comparison of the Fugro Pressure Corer and the HYACE Rotary Corer

The FPC is a percussion corer developed by Fugro in the Netherlands. It uses a water hammer driven by well fluid circulation to drive the core barrel into the sediment ahead of the well bit. As such, it is suitable primarily for sampling in unlithified sediments (muds, sands, and gravels). The FPC acquires a core 57mm in diameter. The FPC was developed by Fugro in the Netherlands. The HRC is rotary corer developed at the Technical Universities of Clausthal and Berlin in Germany. It uses a downhole motor driven by fluid circulation to cut a core by rotating the barrell. As a result it is capable of taking core both in soft sediments and in harder rocks. The HRC obtains a core 51mm in diameter. Both devices are rated to retain up to 3625 pounds per square inch of pressure.

Both devices are supported by a family of pressure chambers that enable the samples to be removed from the corers and transferred to storage, transportation or analysis chambers while retaining full pressure.