A Depletion Planning Model for the Development and Management of Multilayered Gas Fields
Authors: Ismanto Bambang , Weimer Ben 
Published: December 2007

Abstract
VICO's major gas fields in East Kalimantan, Indonesia contain in excess of 2,000 individual gas reservoirs ranging in depth from 4,000 feet to 15,000 feet that have been penetrated by almost 500 wells. These reservoirs are located in a geologically complex deltaic environment and, therefore, vary drastically in size, permeability, and compositional make-up.
Because of the large number of wells and reservoirs, a Depletion Planning (DEPLAN) program was designed, developed, and implemented by VICO to assist managing deliverability, current and future wellbore optimization, and compression requirements necessary to meet gas sales commitments. DEPLAN is a computerized field management program linked to VICO's PARM database. It assembles, organizes and analyzes data using standard engineering principles to optimize field depletion planning. The program utilizes volumetric depletion methodology for gas reservoirs and generates individual well deliverability by combining inflow and outflow equations. The results of simulation models can be entered into DEPLAN as necessary.
The gas requirement schedule and reserves are input parameters, with the model output essentially represented by field gas deliverability predictions and generation of work programs. Since it's inception in 1990, DEPLAN has proven to be a valuable tool to assist in reservoir management and development of complex multilayered gas fields.

Introduction
VICO Indonesia, as a Production Sharing Contractor to PERTAMINA, operates four major gas fields; Badak, Nilam, Mutiara and Semberah which are located in the Mahakam delta of East Kalimantan, Indonesia (Figure 1). These fields provide an average daily supply of approximately 1.5 Bscf/D to the Bontang LNG plant and Kaltim Fertilizer Plants. The four fields consist of more than 2,000 gas reservoirs with the majority occurring in the form of distributary channels and mouth bars. Currently, 467 wells have been drilled and completed in these fields as dual, dual selective or single completions. Typical reservoir and well completions are shown in Figure 2.
Because of the large number of reservoirs and wells with multiple completions, a specific computerized Depletion Planning (DEPLAN) program was designed by VICO to assist in the managing the development of these fields. This paper describes the DEPLAN program and explains its' application in the optimization of development of the Nilam field.

Description of Depletion Planning Model
The computerized DEPLAN program is a field management tool designed, developed, and implemented by VICO to assemble, organize and analyze data using standard petroleum engineering principles to optimize field depletion planning. The program utilizes volumetric depletion methodology for gas reservoirs and generates individual well deliverability projections by combining inflow and outflow equations.
DEPLAN is automatically linked to VICO's engineering, geological, and operations (PARM) database for extraction of numerous tables of current and historical data. Formatted data entry screens are provided for input of necessary criteria such as schedules for gas rate requirement (demand), well producing priority, and well prognosis as well as parameters for timing of certain actions, range limitations for completion, and compressor or facilities capacities. The program output options are essentially presentations of field gas deliverability and production predictions in addition to required work programs over time. DEPLAN's operational flexibility facilitates the evaluation of various producing scenarios with respect to time.
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