TX 75083-3B36, U. S.A., fax 01-972-952-9435. Abstract Identification and distribution of natural fractures are important in development of oil and gas fields. On the basis of detailed observation and description of core fractures and their comparison with advanced imaging well-logging fractures, natural fractures can be distinguished from induced fractures. Due to conventional well-logging responses to the high conductivity of fractures, all kinds of fractures may be recognized. Lithology and lithologic association control on the distribution and behavior of natural fractures under concurrent structural settings, natural fracture distribution is indirectly predicted by searching for lithologic combination, which is implemented by seismic inversion under the control of welllogging quality. In addition, fracture distribution is forecasted by extracting fracture information from compressional wave data after excluding Iithologic factor.

This paper investigates the influence of water level oscillation and sediment supply volume on shallow‐water delta development by means of a flume experiment. The experiment simulated the natural water level by dividing a cycle of sediment period into four parts: the draught period, the flood period (FP), the interflood period in a falling limb (IPF) and the interflood period in a rising limb (IPR). During the FP, flooding broke former channels and a large amount of sediments were evenly unloaded at the surface of lobes. Erosion often appeared at the beginning of the IPF and was dominant at low stand. Most sediments were concentrated in incised valleys and unloaded at the channel mouth to form a new lobe during the falling limb. Erosional channels and lobes were broken at the IPR. Sediments homogeneously covered the surface of lobes and few new lobes appeared during the period. Different sediment supplies influenced the characteristics of incised valley and channel style. Low sediment supply to the delta was strongly influenced by water level change, while high sediment supply was mainly affected by fluvial processes. Based on the flow sand content of water, channels can be classified into four types: (a) narrow and deep multiple channels, (b) narrow and shallow branch channels, (c) broad and shallow main channels, and (d) broad and deep stable channels. Their width‐to‐depth ratios are 1.1–3.5, 5.1–12.9, 7.3–20.2, 2.6–4.6, respectively. Most mouth bars were initially formed but then broken by water level oscillation and channel bifurcation. The preserved mouth bars were well preserved at the far end of lobes, where they entered the low‐energy environment.