Research On Types And Genetic Mechanisms Of Tight Reservoir In The Lucaogou Formation In Jimusar Sag

The reservoirs were commonly tight and fracture-developed in Lucaogou formation of Jimusar Sag,however,the genetic mechanism of fracture was not clear.The character description,recognition,and cause of formation were researched in this paper aiming at the tight reservoirs in the Permian Lucaogou formation by using field observation,core observation,cast section and logging recognition.The structural fractures,diagenetic fractures and abnormal pressure fractures were developed in the tight reservoirs of study formation,among them structural fractures included high-angle and medium-low angle fractures,abnormal fractures consisted of drainage fractures,diagenetic fractures were mainly bedding fractures.Based on cutting relation,rock acoustic emission experiment,Oxygen and Strontium isotope analysis,structural fractures within Permian sand reservoirs in study area were classified into 4 periods,of which the 4th stage fractures were the most valid with highest development and lowest mineral filling degree.The formation of bedding fractures within Lucaogou formation of Jimusar district was related to paleo-structural stress,sedimentation and diagenesis,and acid dissolution caused by hydrocarbon generation,most bedding fissure burst into fractures and oil distributed along the bedding fractures.Two bedding fractures formation modes were summarized based on bedding fractures study in study area: structural-diagenesis cause and hydrocarbon acid dissolution cause.The synthetic evaluation parameter was put forward,a kind of fracture recognition standard and prediction method was established,in this way the accuracy of well profile fracture recognition and fracture system prediction within tight reservoirs was guaranteed.