Research And Application Of Acid Fracturing Technology For Mud-conglomerate Reservoir In Shulu Hollow Of Huabei Oilfield

Huabei oilfield shulu area of dense mud-conglomerate reservoir heterogeneity reservoir,acid fracturing operation of shale content released after acid corrosion problem existed,at the same time,regular crosslinked acid,gelled acid system such as short range and carrier sex difference,low viscosity,filtration,lead to the mud-conglomerate heterogeneity reservoir fracturing stimulation effect is poor.Based on the evaluation of the compressibility of marling-conglomerate reservoir in shulu area,it is concluded that:(1)The influence of maximum and minimum principal stress and stress difference on initiation range in shulu well area is basically linear distribution.(2)Horizontal stress difference is the main factor affecting the fracture initiation range in the shulu well area.(3)In the middle of shulu sag,there are well-developed fractures in the reservoir section of the shasanxia sub-member,and structural fractures are developed in the target layer,which are mainly high angle natural fractures.Most of the fractures are filled with calcite or without filling.(4)The rock mechanics parameters in the shulu well area reflect that the brittleness index of the target layer is in the multi-fracture-fracture network transition zone,with ideal conditions for transformation.Based on the study of the mechanism of marling-conglomerate network fracture formation,it is concluded that the main influencing factors are horizontal stress difference,natural fracture development and rock mechanics parameters.Engineering from the construction capacity,viscosity of fracturing fluid,fracturing scale and pump injection program to adjust,seam proppant transport network is difficult,perhaps even a sand plug,so should strictly control the proppant concentration and dosage,increase the proportion of small particle size of support and appropriately,and uses the multistage composite particle size,in the different area of the joint network to form effective support.In view of the problem of the release of argillaceous content after acid-etching of marling-conglomerate in the shulu area,it should be ensured that the liquid has good viscosity-temperature performance at high temperature,slow reaction rate of acid rock and certain carrying capacity.The screening principle of acid system in marling-conglomerate reservoir is to reduce the amount of argillaceous attachment and delay the reaction rate of acid rock.The clean acid system is characterized by low reaction rate of acid rock,good ability of acid corrosion fracture flow diversion,strong shear resistance,less shale on rock surface after the reaction,small friction and good effect of breaking glue,etc.Therefore,the clean acid system is more suitable for the marling-conglomerate reservoir in shulu depression.The main factors influencing the fracturing effect construction volume,viscosity of fracturing fluid,perforating way,acid carrier and proppant selection.As a result,the site should be as far as possible,improve construction capacity,rapid pressure-out produce cracks,adopt multi-stage combination of proppant size in different area of the joint network effective support,selection of low stress interval perforation,so that the crack and the extension of crack.The pressure drop curve analysis can be used to identify the characteristics of fracture propagation and the communication between fractures and reservoirs.The construction of well shuyuanyu1 shows that the complex multi-fracture system rather than the complex fracture network system is easy to be formed in shuolu oilfield.In the future,the transformation direction should be adjusted from the complex fracture network system to the formation of the complex multi-fracture system.