4-D seism

also known as time-delay 3-D seism

is a new technique for reservoir development and management. Its main task is to study the differences between time-delay 3-D seismic data caused by fluid changes in reservoirs. So time-delay seismic data must have repeatability or identity. Be combined with well and development history data

4-D seismic data can provide more accurate reflection cocfficient

temperature

pressure

productivity capacity and fluid changes of reservoirs. This technique can also improve recovery rate and well-drilling success ratio. But it must be pointed out that this technique is not suitable for all reservoirs. It only suitable for the reservoirs whose pore fluid

rock compaction and pressure change considerably

the net-overload pressure is small and reservoirs are buried shallower

and there are seismic differentiae in given range of seismic resolution of reservoirs

synthetic effect. In order to gain its proper economic benefit

the operation of 4-D seism will be carried out into three stages:1. feasible study

2. forerunning test in site

and 3. oilfield application on a large scale. At present

all successful examples of 4-D seism focus on forerunning test.