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 oil -in-place in the development stage

The reserves of “A” gas fields were evaluated as a part of oil development project evaluation. It consists of three fields of X, Y, and Z, and the size is about 10 km long and about 5 km width. They are anticline structures accompanied by the fault.

◆For the simple anticlinal field, calculation of original oil-in-place by the volumetric method

It is carried out as follows for the analysis of reservoir characteristics. Porosity was calculated by crossplotting method of density and neutron logs. Water saturation was estimated by the Shimandoux equation because the reservoir includes shale. Reservoir areal extent and effective thickness were evaluated by the net pay map based on the well correlation results. From the above information the original OIP was calculated using volumetric method.

After calculating original OIP, the validity of the development plan was evaluated based on the prediction of production performance through reservoir simulation for the constructed reservoir model.