HYDRAULIC FRACTURING GAIN EVALUATION USING MINI-DST AND POST-FRACTURING PRESSURE BUILD-UP: A CASE STUDY IN LOW PERMEABILITY GAS CONDENSATE RESERVOIR

摘要

Sisi and Nubi are two gas fields located 25 km offshore the modern Mahakam delta (Mahakam PSC, East Kalimantan). These fields consist of multiple reservoirs with different geological environments. The main reservoir corresponds to fluvio-deltaic and shallow marine deposits. In the Sisi field the deep reservoirs of "Sisi Main Zone" have low permeability and concomitant low productivity, therefore hydraulic fracturing is necessary to increase their productivity. Pre-fracturing and post-fracturing downhole data acquisition was performed to estimate the well productivity improvement and to quantify the gain (incremental reserves) brought by the hydraulic fracturing job. Mini-DST using dual Packer was done to evaluate reservoir permeability. The test yielded a satisfactory permeability assessment and confirmed the phi-k law as well as permeability anisotropy. Nodal Analysis before hydraulic fracturing was used for well test design. This methodology has been tested and proved on analog wells. The well was fractured and put on production; Back Pressure Test and Pressure Build-Up (BPT-PBU) were recorded after the operation providing accurate productivity estimation. In order to avoid proppant flowback, a limited drawdown was applied and then the well was producing at a gas rate higher than estimated production without hydraulic fracturing. To evaluate the overall gain, a single well model is created using Material Balance with Nodal Analysis by controlling the simulation using Tubing Head Pressure.