HORIZONTAL WELLS AS A SOLUTION TO PRODUCE GAS BEARING LOW PERMEABILITY SANDS IN THE G ZONE RESERVOIRS OF THE TAMBORA GAS FIELD, EAST KALIMANTAN, INDONESIA

摘要

Tambora Field, located in the Mahakam Delta, East Kalimantan, is a gas field with some small oil accumulations discovered by Total E&P Indonesie in 1974. The reservoirs are fluvio-deltaic channel and bar sands intercalated with shale and coal layers. The pay zone is subdivided into 4 zones: the D, E, F, and G zones. The G zone has the poorest reservoir quality in terms of porosity and permeability, and has the lowest productivity. A number of vertical wells were completed in the G zone and yielded marginal productivity, either in rate or production duration, before the wells were recompleted to the shallower, and more producible F, E, and D zones. In 1998 a horizontal well was drilled with a 400 m lateral section length in a G zone reservoir. The well has produced 15 BSCF as of year-end 2002 with an average production of 10 MMscfd. In 2001 a second horizontal well was drilled within the G zone reservoir and as of year-end 2002 has produced 6.5 BSCF and averaged 10 MMscfd. In November 2002, a bi-lateral horizontal well was drilled to a G zone reservoir. The well had a lateral section length of 600 m and has averaged 30 MMscfd as of year-end 2002. Based on the results of these three horizontal wells, a new plan to develop the tight G zone reservoirs with horizontal wells is being proposed. The remaining potential in the D,E and F zones will also be developed with a combination of shallow and deep vertical wells with the aim to optimise the development of the field.