An Enhanced Seismic Attribute as a Different Perspective to Identify Carbonate Bulid-Up Reservoir: Case Study Mila A-01 Well, Mila Field, Southeast Sumatera, Indonesia

Abstract

Mila Field is located at Southeast Sumatera Block of the CNOOC PSC. This field was discovered in 1982, with 5 (five) exploration wells i.e.: Mila-1, Mila-2, Mila-3, Mila-4, and Ratna-1. The reservoirs are Gita-A and Gita-B sandstone, Talang Akar Formation. Mila A-01 is proposed as development well to recover gas reserves in Gita-A sandstones originally found by Ratna-1. Other objective is to test the existence of Lower Baturaja Reef identified by the latest seismic attributes that was formerly not found by Ratna-1 and relatively “undetected” by other seismic classes. This field is covered by Gas 3D seismic survey in the southern part within ±7,521 acre area. Play type of this field is structural and stratigraphic trap, or combination both of traps with reservoir from Upper Gita sandstones of Talang Akar Formation. Based on latest seismic re-interpretation, seismic attribute analysis has been conducted and found anomaly as a prospect area ±520 m southwest of the exact Ratna-1 location, identified as Lower Baturaja Reef (LBR). Ratna-1 did not encounter this LBR Reef because the well location is right at the edge of this LBR Reef. The Reef as a carbonate build-up is sitting directly above the Gita-A. A newly enhanced seismic attribute has the highest resolution using PSTM seismic data class to identify carbonate build-up compared with other seismic classes. The body of the porous gas bearing reefal carbonate is seen as a high amplitude peak on the PSTM seismic volume. This peak merges by down lap with the top Gita-A event at the limits of the reef. The clustered carbonate build-up at LBR Reef is well illustrated using Acoustic Amplitude, Ratio Positive to Negative, and Sum Amplitude Attributes. Mila A-01 well was spudded on April 17 2014 and Elan log shows the well encountered a total of 24′ TVD of net gas pay with average porosity of 24.3% and water saturation of 37.7% in the LBR Reef. Mila A-01 well is a proven case that enhancement in the seismic attributes could lead to discovery of Lower Baturaja Reef in Mila Field.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015