The extended reach horizontal well drilling technology suitable for shallow layers in Dongfang 1-1 Gasfield

The shallow reservoirs in Dongfang 1-1 Gasfield are in the middle and late stage of development. Due to the restriction of offshore platform space and well slot quantity, the potential tapping of remaining oil and gas in the periphery of the platform is mostly carried out in the mode of "external additional well slot+extended reach well" or "old well sidetracking+extended reach well". The shallow formations in this area are unconsolidated, and together with the effect of pile group, channeling and leakage tend to happen at the surface pile casing shoe and well trajectory control is difficult. Besides, the reservoir pressure in this Gasfield is depleted. As a result, the complicated downhole accidents happen frequently in the process of early drilling, such as pipe sticking, casing sticking and lost circulation, and the drilling time efficiency is lower than 70%. A series of technological researches were carried out in terms of surface riser type selection, drilling fluid plugging and lubricating performance improvement and fine well trajectory control to solve these problems. In 2016, the research results were applied in 4 extended reach horizontal wells on X4 platform in Dongfang 1-1 Gasfield. Thus, a set of extended reach horizontal well drilling technology suitable for the shallow layers in Dongfang 1-1 Gasfield were ultimately developed after further improvement. In 2017, this technology was applied in one horizontal well with horizontal displacement of 4 107 m and horizontal-to-vertical ratio of 3.119 on X1 platform in Dongfang 1-1 Gasfield. No leakage or complex downhole situations occurred in the whole process of drilling and the drilling time efficiency was increased to 99%. The research results provide the technical reference for the construction of similar wells in Dongfang 1-1 Gasfield.