The Investigation On Bottom Water Coning In Horizontal Well

Horizontal well is effective in exploiting field, which can bring all advantages into full play, such as larger drainable area, control bottom water rising, improve flat connectivity remarkably, enhanced oil recovery, save invest for well drilling. In high permeability reservoir, remaining oil at the top of thick oil layer has been exploited by horizontal well in the old liberated area of Changyuan Daqing city, which developed a horizontal well applied frontier. But it brought complicated reservoir engineering problems. We chose the area as research background and researching for bottom water coning in horizontal well.First of all, based on hydrostatics theory, analyzed formation mechanism and defined stable conditions of corning. By combining it with flat radial direction time invariant seepage theory can define streamlines distribute, breakthrough time, critical produce, critical length, bottom water's displacement efficiency and shape of coning in bottom water layers. Reveals the following regularities:(1) After calculating the streamlines distribution of horizontal well bottom water coning by stream function. For bottom water reservoirs, We can find that the smaller reservoir thickness is, the keener bottom water streamlines distribution are, vice versa. If the reservoir thickness is infinity, bottom water streamlines distribution approach edge water case.(2) We can got the peak moving regular of water coning by potential function. The movement velocity of peak is incremental in coning water formation process, the closer to horizontal well borehole, the faster it is. It is important to control coning at the early phase. At particular time, vertical permeability is inversely proportional to water coning time, the smaller it is, the longer breakthrough time is. Reservoir thickness and water coning time in direct proportion, the bigger reservoir thickness is, the longer breakthrough time is.(3) For laminar flow, water ridge of horizontal well which is large duty and longer is flat (at this time, the whole horizontal well breakthrough), water ridge of horizontal well which is low duty and shorter is aciculate (at this time, the middle part of horizontal well breakthrough). If the horizontal well has very high output, the affect of borehole tube current are larger, the place of breakthrough will deviate to heel.(4) With horizontal well length increasing, displacement efficiency function will add (not think about borehole tube current). With well length reach a specified value and thinking about borehole tube current, displacement efficiency function will to be a constant.Based on theoretical analysis, we chose the canonic well as an example to be analyzed, which can offer innovation to high water cut stage horizontal well disposition at the top of thick oil layer in old liberated area outer-ring.