Material balance models in production forecasting

Whenever we make a production forecast, we use a model of the reservoir and production system, whether it be in the form of a simple mathematical equation (e.g. decline curves) or a full-field 3-D simulation model with surface networking. But no matter how complex the model, it is always a simplification of reality. The aim of the forecaster, in making reliable predictions, is to use a model that is sufficiently representative of the physical processes and constraints, and that adequately allows, on a resource-benefit basis, for treatment of uncertainty in the input and output of the model.

Somewhere in the spectrum of modelling techniques, material balance plays an important role; either in supporting a more complex model (e.g. ground-truthing results) or as the principal methodology for producing forecasts. Material balance treats the reservoir as a tank (or limited number of tanks) with uniform properties. Other than what is required to calculate volumes, there is limited geological input. This lends simplicity and practicality but at the same time limits the applicability in more complex reservoirs. This chapter describes the potential uses of material balance, when to use the technique and offers practical guidelines on its use.

What is material balance

General description of the technique; inputs and outputs, what can and can’t be modelled. Vertical Lift / Surface networks.

Uses of material balance

Reservoir performance, performance-based verification of reservoir / aquifer / gas cap volumes,

When to use material balance

With the increased capability of and accessibility to high-powered CPUs, the default option of the reservoir forecaster today is to build a 3-D simulation model. Whilst this often gives the impression of rigour and can look impressive to the less scientifically-inclined, the use of a simulation model may be overkill. It requires additional input that may not add to the representativeness of the model and, furthermore, may not be supported by reliable / available data. At the same time, this modelling route invokes a significantly increased resource and time cost that may detract from producing a reliable forecast. Material balance should always be considered early as a modelling option on the route to generating production forecasts.

Based on complexity of reservoir (permeability variation), complexity of reservoir fluid system ( oil vs gas, single vs multiphase) and complexity of development plan. Data availability (geological and performance data) and uncertainty. Time/resources availability. Is surface network modelling (e.g. in a gas-field complex) the most important determinant in production performance?

INSERT Reservoir Heterogeneity (Pending permission approval)

Forecasting guidelines using material balance modelling

Summary guidelines on how and when to use. List of 10 to 15 bullet points

Noteworthy books

Society of Petroleum Engineers (U.S.). 2011. Production forecasting. Richardson, Tex: Society of Petroleum Engineers. WorldCat or SPE Bookstore

See also

Production forecasting glossary

Aggregation of forecasts

Challenging the current barriers to forecast improvement

Commercial and economic assumptions in production forecasting

Controllable verses non controllable forecast factors

Discounting and risking in production forecasting

Documentation and reporting in production forecasting

Empirical methods in production forecasting

Establishing input for production forecasting

Integrated asset modelling in production forecasting

Long term verses short term production forecast

Look backs and forecast verification

Material balance models in production forecasting

Probabilistic verses deterministic in production forecasting

Production forecasting activity scheduling

Production forecasting analog methods

Production forecasting building blocks

Production forecasting decline curve analysis

Production forecasting expectations

Production forecasting flowchart

Production forecasting frequently asked questions and examples

Production forecasting in the financial markets

Production forecasting principles and definition

Production forecasting purpose

Production forecasting system constraints

Quality assurance in forecast

Reservoir simulation models in production forecasting

Types of decline analysis in production forecasting

Uncertainty analysis in creating production forecast

Uncertainty range in production forecasting

Using multiple methodologies in production forecasting