Design And Research Of Acid Fracturing For Low Geophysical Segment Of Heavy Oilfield

Heavy oil reservoir generally has four geological characteristics:big change of reservoir buried depth and large thickness variation,good reservoir property,poor physical properties of crude oil and more types of reservoirs.L reservoir was discovered in the early 1970 s.After the success of the steam stimulation test in 1982,the steam stimulation technology was fully developed after 1985.The production of heavy oil in L decreased in 2005,The main reason is that the oilfield which adapt heavy oil mining technology of steam injection is close to exhaustion and more complex strata require more advanced mining technology.Therefore,heavy oil recovery technologies such as steam flooding,steam assisted gravity drainage,non-hydrocarbon miscible flooding and so on have been started.However,for some special strata,corresponding effective techniques need to be carried out.Acid-fracture technology has played an important role in the development of L heavy oil field.It has increased cumulative production about 1.03 million tons,accounting for 39.9% of the cumulative reserves,which is one of the key development matching technology.Based on the block which is developed low geophysical segment in L heavy oil reservoir,this block has some characteristics such as multilayer,low permeability of the low-permeability layer.In the early stage,steam stimulation had been carried out,later transferred to steam assisted gravity drainage,it has no effect or poor effect on perforating the low-permeability layer for steam injection well on two occasions.Therefore,it is proposed to transformation the low-permeability layer by acid-fracture technology.In view of the problems above,this paper will adopt reservoir engineering method and reservoir numerical simulation method.First of all,3D geological model and numerical model should be established,and history matching of the whole area and the single well must be completed.At the same time,low geophysical segment should be re-recognition.The influence of low geophysical segment of different attribute on steam cavity expansion and sweep efficiency is analyzed.Finally,the type of low geophysical segments for the block is reclassified by properties,thickness,breakthrough time and so on.Then,using numerical simulation method,the influence of acid fracturing technology on development effect of SAGD is analyzed from some aspects of flow conductivity of the cracks,oil incremental effect,the influence of steam cavity expansion and the effect of sweep efficiency,and the effect of the low geophysical property of different thickness and permeability on steam cavity expansion and sweep efficiency after acid fracturing is studied.Finally,aiming at differenttypes of low geophysical properties,the effect of acid fracturing is predicted from daily crude output of a single well,cumulative oil production of a single well and water cut of a single well.