Abstract

The Jatibarang field has several shallow sedimentary pay zones, but the major production zones are in the deeper naturally fractured volcanic formations. Given this unusual lithology profile, wells drilled in this area experience frequent problems, notably hole instability, excessive reaming, stuck pipe, and lost circulation. The causes of such problems are generally thought to be related to reactive shale layers and the porous and permeable hydrocarbon bearing zones which lie just above the fractured volcanic formation.

As the field is located within the rice producing areas of West Java, economic and environmental restrictions dictate that the wells are drilled in clusters of up to seven wells from a single surface drilling pad to minimize disruption. Thus, during the drilling of this field, lower than expected formation pressures are encountered due to a depletion effect caused by the proximity of the nearby wells.

Reactive shales, differential sticking in the permeable (depleted) layers, and severe losses into the fractured volcanic zones were all problems encountered in previous wells, where traditional lignosulphonate muds were used. A newly introduced modified Mixed Metal Hydroxide (MMH) drilling fluid that is reservoir compatible, environmentally benign and has a unique rheology, was utilized for drilling JTB-201 in an effort to overcome these problems.

The unique rheological profile of this MMH fluid, along with its apparent inhibitive behavior, are considered strong and positive contributing factors to drilling successfully through reactive shales and permeable zones to the fractured volcanic zones, while maintaining adequate shale inhibition, curing lost circulation, and preserving well integrity at all times. It is this new and unique combination of traditional MMH rheology, coupled with increased inhibition, that has achieved very successful drilling performance across this fields' complex lithology.