Identification and prediction of gravity flow channel interlayers under deep-water and few-well conditions

ObjectiveThe X gas field of Lingshui in Qiongdongnan Basin has proven natural gas reserves of 12.809 billion cubic meters. However, oil and gas exploration has been hindered by challenges such as the large water depths of the offshore basin, limited well data, low resolution of seismic data, and unclear identification of interlayers, thereby failing to meet the requirements of oil and gas exploration. This study aims to address these challenges by establishing identification criteria for interlayers and optimizing the oil and gas development plan of the X gas field of Lingshui. MethodsThis research utilized core samples, well logging data, and seismic data, which were used to create a set of criteria for identifying interlayers in the Huangliu Formation's gravity flow channels. Additionally, frequency extension and seismic inversion techniques were employed to reveal the distribution patterns of interlayers with different genetic origins in the gravity flow channels of the Huangliu Formation, thus providing a basis for the optimization of oil and gas exploration and development deployment. ResultsThe results indicated that: (1) The overall sedimentary system in the study area was a canyon-channel system, characterized by the development of five distinct microfacies: Gravity flow channels, channel-levee complexes, sheet sands, slump deposits, and deep-sea mud. (2) The Huangliu Formation contained mudstone interlayers, mudstone interbeds, and calcareous interbeds. Mudstone interlayers and mudstone interbeds show the characteristics of high natural gamma ray values, high density, moderate acoustic travel time, and low resistivity, while calcareous interbeds were distinguished by low natural gamma ray values, high density, low acoustic travel time, and high resistivity. (3) Mudstone interlayers predominantly occurred in the external and marginal areas of the canyon, forming a large-scale stable distribution, while mudstone interbeds were confined to small, local areas on the flanks of the canyon channels. Calcareous interbeds have a small distribution area and poor stability. (4) The development of these interlayers was influenced by the sedimentary microfacies. When the gravity flow energy was strong, interlayers were more commonly found in the levee mud deposits along the channel sides. Conversely, when the energy was low, interlayers were dominated by deep-water in-situ deposits. (5) An optimized deployment plan and well trajectory for the newly developed Well A-1 were proposed, leading to the establishment of a semi-quantitative prediction techniques for interlayers, which improves support for subsequent oil and gas exploration and development. ConclusionIn conclusion, the results of this study provide significant theoretical and technical support for the identification, prediction, and subsequent oil and gas development in X gas field of Lingshui and similar deep-water gas fields. The technical methodology established in this study is expected to improve the exploration efficiency and optimizing the development strategies of deep-water hydrocarbon reservoirs.