Omer Inanc Tureyen

Effect of the wellbore conditions on the performance of underground gas-storage reservoirs

This paper presents results of an underground gas storage modeling study using the reservoir and fluid properties of the Northern Marmara gas field, a recently developed field in the Thrace region of Turkey. It has an area of 3.6 km 2 with nearly 3 billion sm 3 of GIIP The reservoir model used in this study is based on the theoretical as well as the empirical deliverability equations. The deliverability equations reflect the production and injection performances of the wells with given completion characteristics. Our approach is based on maximizing working gas volume for a particular configuration of reservoir, well and surface facilities. The importance of the type of well completion was emphasized in this paper because this is the most likely place for operating problems to occur. The deliverability performance strongly affects the design factors such as the corking gas volume and the number of wells operated. Results indicate the performance dependence on wellbore damage and hence the importance of cleanup of wells. The effects of the mechanical skin factor on the working gas capacity with different number of horizontal wells as well as vertical ones were studied. Results show that the working gas capacity decreases while the mechanical skin factor increases. This behavior becomes especially more dramatic as the horizontal well lengtl decreases. The increasing number of wells increases the working gas capacity as expected. These results are discussed in detail through application to N. Marmara gas reservoir data. The underground gas storage modelling approach followed in this study is shown to be an effective way to forecast the production / injection performance and to estimate the important design parameters when converting a depleted gas reservoir to a gas storage reservoir. Our approach yields the better understanding of the effect of the wellbore conditions on the performance of the underground gas storage reservoirs as well.