East China Sea discovery opens channel play

By OGJ editors
HOUSTON, June 2 -- Primeline EnergyHoldings Inc., London, said its Lishui 35-3-1 exploratory well is a hydrocarbon discovery that opens a channel play in the west flank of the West Lishui basin and had the first gas flow from a low permeability reservoir in the southern East China Sea.

The discovery, on Block 25/34, also has important implications for development of Lishui 36-1 gas field which Primeline and China National Offshore Oil Corp. are jointly developing.

After logs indicated a combined 20 m of potential hydrocarbon pay in two zones, Primeline engaged China Oilfield Services Ltd. to run drillstem tests.

The first DST, at 2,836-52 m measured depth with diesel, yielded no flow of hydrocarbons to surface.

On another DST at 2,794-2,802m MD with nitrogen, gas flowed naturally to the surface and was flared continuously and steadily for more than 7 hr. A second flow period was attempted after an 18-hr shut-in but was unsuccessful because formation sand blocked the test valve. A second 15-hr shut-in period followed.

Data from the downhole pressure gauges showed that the two pressure buildups during the shut-in periods were consistent. The surface gas flow during the first flow period was at a low pressure that steadily rose over the 7-hr flow period but did not reach the pressure necessary to operate the separator or the flow meters. The well’s flow potential was thus not measured.

Gas samples were collected at the wellhead and fluid samples were collected from the wellbore to be analyzed in laboratory conditions. It was therefore decided that sufficient data has been collected to enable the estimation of the production pressure and flow rates and the composition of the hydrocarbons in due course.

The test program ended on May 29, and the COSL rig will be released in the next few days after the completion of current end-of-well operations.

Three channel systems have been mapped and delineated in Primeline’s 3D seismic area, and others have been recognized to the north of that area which is covered by 2D seismic.

Primeline will carry out a careful post well evaluation over the next 4 to 6 months to assess the volume and nature of the resources discovered in LS 35-3, refine the petroleum system model and high-grade and further define prospects for further exploration drilling.

The LS 36-1 gas field has more than 200 m of gas-bearing, low-permeability reservoirs directly below the gas zone being developed. With the new data from LS 35-3-1, Primeline will assess the potential for modern hydraulic fracturing and horizontal and multilateral drilling technology to make the low permeability reservoirs achieve commercial production rates.

The LS 35-3-1 discovery well is 14.5 km from the production facility to be built at LS 36-1 and could be tied in at relatively low cost.