Estimation of Original Oil-in-Place in the Development Stage｜Asia Oceania
Oil and Gas Development Consulting and Engineering Company, Japan Oil Engineering

◆First of all, OIP estimation for the asset evaluation of oil and gas fields

The sufficient economical reserves of oil and gas are expected in order that the oil and gas fields become an exploration and development target as a commercial activity. Therefore, we calculate whether exists how much oil and gas in the mineral deposits underground through the reserves evaluation. Two of the calculation method of the deterministic approach and stochastic approach are used in the reserves estimation and the applicable calculation method at each stage of exploration and development will be different. Furthermore, the reserves evaluation is needed for the verification of the validity of the updated data in reservoir modeling work. In addition, reserves held by oil development companies, has been important from shareholders and investors as one of the index representing the corporate strength of the company. Therefore, the assessment of the precise reserves by the appropriate calculation method is the essential processes in terms of the success of projects related to oil exploration.

◆Evaluating 109 oil and gas reserves in the past 10 years

JOE has been carried out a reserves evaluation of oil and gas fields in the projects amounting to 109 in countries and regions for trading companies, banks, electric power companies and oil companies during the past 10 (2005-2015) years.

Resource development of crude oil and natural gas proceeds with the exploration⇒development⇒production. In the Southeast Asia relatively close to Japan, there are a lot of “production project” and “development project” which produce most likely cash flow in the current or near future.

◆Estimation of original gas-in-place in the development stage

This project is the original gas-in-place(GIP) evaluation of B gas field in the Southeast Asia where both of Structural and Stratigraphic type traps are identified. Trapping mechanisms are not only structural traps originate in the geometric arrangement of strata like anticline or domal structures but also stratigraphic traps like pinchout due to the lateral lithological change and discontinuity caused by the unconformity. The data acquisition of the reservoir heterogeneity is of important to find this kind of the stratigraphic traps.

There are some seismic attributes as the techniques that can be used to estimate the distribution and heterogeneity of such reservoir rock, in this case considering the distribution of the gas reservoir from amplitude anomaly of the seismic reflection wave. Thus by using suitable method for each structural/stratigraphic trap with particular consideration of the uncertainty of stratigraphic trap we estimated the GIP based on the analysis incorporating the probabilistic approach.

In this case a production profile was made so that the cumulative total production was equal to recoverable reserves using gas reservoir model incorporating the material balance method and gas deliverability equation.