It has been a huge challenge to generate type well curves for UR plays due to the reservoir heterogeneity, complicated fracturing mechanisms, different completion designs, and production operations. The industry has been trying to use analytical, statistic, and numerical modeling methods. Complexity of fracture networks limits the usage of analytical method, and lack of physics mechanisms and long-term production data constrains the application of statistic method. Numerical method often requires significant resources and expertise.
This paper will illustrate a practical approach to generate robust type well curves.
For a given geologically similar area (GSA), we build a sector numerical model, and then calibrate the model with available production history with assistance of automatically-history matching method.
Identify the key uncertainties and investigate their possible ranges.
Study the effectiveness of past completion designs and investigate the possible completion designs.
Perform multiple runs with Monte-Carlo simulation method based upon the ranges and the distribution types of those uncertainties and completion design parameters.
Compare the modeling results with the real production data from the same GSA, and perform multiple runs again by adjusting the ranges and/or distribution shapes of the those uncertainties if needed.
Build type well curves based upon the calibrated multiple runs.
We have applied the workflow and built multiple type well curves for several GSAs of those URs in the Permian Basin. The automatic process of history matching and forecasting significantly reduces the manpower requirement. Since the approach enables us to incorporate the different flow mechanisms, formation heterogeneity, and completion designs, we observed that the outcomes of multiple runs from those calibrated models are very consistent with well production historical behaviors. We witnessed that the workflow was very easy to follow, and less experience engineers were able to generate those type well curves very efficiently.
Our practical workflow is very easy to follow and can be applied into various UR plays in different basins. The effective approach enables us to easily integrate various physics flow mechanisms in the unconventional reservoirs with various completion designs. Therefore, the resulting type well curves should be more reliable to forecast the overall performance of multiple wells in a given geologically similar area. It is very convenient to develop type well curves for a subset of the GSA or completion designs, which enable us to get into the critical and insightful information about the subsurface and/or completion effectiveness.