Abstract: There are quite a few horizontal wells featuring insufficient logging suite,and thus are difficult to evaluate.However,the way to effective evaluation on horizontal wells with limited logging data is of great significance to successful development of gas reservoirs.We propose a productivity evaluation method based on two parameters,which are the peak value of Gamma ray logging and the effective total hydrocarbon indicator,because for many horizontal wells in the drill sector X of Daniudi gas field in Ordos Basin,only Gamma LWD and gas logging data are available.In addition,the method proposed also employs some of the dynamic geological and production data.It effectively improves the accuracy of productivity evaluation on horizontal wells,and may be applied to logging evaluation on horizontal wells in gas reservoirs of similar type.The study shows that the Gamma peak value is an effective indicator of reservoir quality:for the reservoirs in Shanxi and Lower Shihezi Formations of the Daniudi drilling sector X,the LWD Gamma data of high production wells are characteristic of single peak statistical distribution,while that of low production wells shows double peaks or no obvious peak,which is largely related to the stability of sand bodies encountered in drilling wells.Furthermore,using the gas logging data in the drilling sector X,we evaluated the single-well productivity based on the effective total hydrocarbon indicator,and propose a gas logging indicator for commercial productivity of horizontal wells in the Shanxi and Lower Shihezi Formations.By integrating these two indicators,we established the dual-parameter evaluation method for horizontal well productivity,and made an accurate prediction on the single-well productivity of the horizontal wells in the drilling sector X.

Key words: horizontal well, total hydrocarbon value, Gamma logging while drilling, well logging evaluation, tight sand gas reservoir, Shanxi Formation, Xiashihezi Formation, Daniudi gas field, Ordos Basin