Numerical Study On Steam Injection In Horizontal Well

Horizontal wells steam injection is an important way to exploit heavy oil in our country,the benefit of which,to a large extent,depends on the bottom steam quality of wellbores and diffusion laws of steam in oil reservoirs.Thus,numerical study on thermal dynamics of steam flow in horizontal injection wells is of certain practical significance.This paper conducts a study on two-phase flow in steam injection wells.Five methods are chosen to calculate friction pressure drop and are compared with field data.The study shows that both Friedel method and B-B method can be used to obtain relatively ideal results.For steam flow and heat transfer in wellbores of different injection schemes,thermodynamic parameters-calculation models of sections prior to horizontal ones of concentric dual-tubing injection,parallel dual-tubing injection and parallel three-tubing injection are established.Then calculation programs are written to obtain distribution rules of steam thermodynamic parameters along wellbores and sensitivity analysis of steam parameters of wellheads is conducted.Furthermore,for parallel multi-tubing injection,effects of heat transfer methods of wellbores and tube sizes on heat dissipation of wellbores are studied.The results show that the proportion of radiative heat transfer is much larger,the decrement of steam injection tube sizes can weaken radiative heat transfer,and chrome plated oil tubes can be used to reduce exterior emissivity of steam injection tube,thus,heat loss of wellbores can be reduced.Wellbores combined with hole arrangement witch put steam into oil reservoir uniformly are studied,the relations between steam flow of orifices and orifice radius,steam pressure,steam quality,pressure difference between inside and outside of oil tube are studied.In consideration of variable mass flowing characteristic of steam in horizontal wells,flow and heat transfer models of steam in horizontal wells are established.Then calculation programs are written to obtain steam parameters distribution in horizontal wellbores and distribution of bottom steam.On the basis of flow and heat transfer models of steam at horizontal sections,sensitivity analysis of steam injection parameters of horizontal wells is conducted,the results show that the increment of steam injection rate can improve bottom steam quality.Moreover,the steam injection effects of horizontal sections are analyzed,steam flow rate and distribution of thermodynamic parameters along steam direction are compared under conditions of orifice size and distribution of different horizontal wells.The study shows that at a relatively low steam quality,even steam distribution is more difficult to be designed,however,it is much easier to inject steam with high quality.