Date of Graduation
Statler College of Engineering and Mineral Resources
Petroleum and Natural Gas Engineering
Most existing gas storage fields have been developed from depleted natural gas and oil production reservoirs. It is not uncommon for gas storage fields to be developed in water bearing aquifer zones where the presence of conventional type reservoirs is limited. Natural Gas Condensate reservoirs are typically not found in the eastern United States where most gas storage facilities are developed close to the colder market and increased population centers. Therefore, data is limited on how the lean dry storage gas will interact with the remaining residual gas condensate liquid and wet gas at reservoir pressure and temperature conditions.;Data concerning fluid analysis and production records can be somewhat difficult. Gas Condensate reservoirs contain multi-component hydrocarbon mixtures that require equation of state models to predict phase behavior under differing conditions. Therefore, adequate initial gas and liquid sampling is necessary that can then have laboratory PVT analysis performed to establish fluid properties such as (dew point, z-factor, viscosity, oil relative volume, etc.). Obtaining this data can sometimes be a challenge due to divesture company's poor recordkeeping and not wanting to incur the expense of extended analysis. Also, acquiring accurate production history records on the liquid and gas production volumes can sometimes be difficult to obtain and assimilate.;Another objective of this study and research is to look at some of the development challenges in the conversion of a gas condensate reservoir to gas storage and how these challenges affects the overall design in storage facilities.;In this study compositional reservoir simulators coupled with equation of state models was used to evaluate a natural gas condensate reservoir under storage development and operating conditions. The Equation of State (EOS) models was used to perform initial fluid analysis and compare to what laboratory data is available to initialize the reservoir fluid set in the model. The compositional reservoir simulator was then built utilizing a certain geologic characterization for the reservoir properties. The phase behavior model can then be used along with the reservoir simulator to validate the primary production history matching and then perform storage scenario analysis.;After an accurate compositional reservoir model was developed and the model has validated the original production history, the storage scenarios were simulated to look at how well configurations and rate profiles affect mixing and the impact on condensate yields.;Since this project will be in service and operating, the actual storage operating data can be integrated into the reservoir design model to further enhance the predictive capabilities of the reservoir model. It is estimated that full development will take several years allowing the model to be calibrated and improved over time.;When a gas storage field is developed, typically there is a need to drill more active injection and withdrawal wells to meet the deliverability design parameter. When a field is discovered there is no immediate need to drill excess wells into the field when for production purposes a few wells will suffice. However, when a gas storage field is being developed depending the areal extent and volume of the reservoir a significant number of new wells may be required to meet the deliverability design. When the wells are designed they can be completed in three ways: vertically, directional and horizontally. Each completion has its pro and cons that need to be considered and with a condensate depleted reservoir more emphasis needs to be placed on how the individual well completions will affect field deliverability performance and residual condensate recovery.;Another consideration in the development of storage is an accurate prediction of the condensate yield rates and the ultimate condensate recovery under gas storage cycling operations. This is important due to the requirement to build adequate surface facilities and project the anticipated yearly condensate production. After a reliable composition reservoir simulator was built the reservoir properties were adjusted to evaluate the impact the storage scenarios have on mixing and condensate recovery. With the calibrated model the effects of resident time on fluid diffusion as a result of mixing were evaluated.;The reservoir simulator was able to predict the impact of surface facilities on condensate recovery and gas deliverability. Condensate blockage around the wellbore is a common problem with mature condensate fields. The wellbore representations in the model were evaluated for the effects of this problem on storage operations.;The reservoir simulator was also used to optimize the number of wells needed to achieve the desired storage field design requirements. The simulator was used to estimate the number of years that condensate production will be a limiting factor in reaching 100% storage field development. (Abstract shortened by UMI.).
Brannon, Alan Wallace, "Prediction of the effects of compositional mixing in a reservoir on conversion to natural gas storage" (2011). Graduate Theses, Dissertations, and Problem Reports. 3032.