Reservoir Precise Desceiption And Researching On The Redevelopment In Gao21Block

The Gao21block is a heavy oil reservoir with a thick sandstone layer in Liaohe oilfield.Since development, it has been mainly relied on steam stimulation. Due to the low reservoirpermeability, higher oil viscosity and clay content and other reasons, there were the problemsof low yield of production cycle and poor development effect in vertical wells. In addition itsproduction rate was low and the recovery factor could not reach the standard value becausethe reservoir was severely inhomogeneous in vertical and the exploitation of each thin layerwas unequal. In this paper, the author studied on the structure, sediment and reservoircharacteristics of the oil layers in Gao21block, and carried out further logging evaluation atthe same time. In order to complete these works, the author comprehensively utilizedsequence stratigraphy, structural geology, sedimentary petrology and reservoir engineeringmethods, combining with the data of drilling, logging, and three-dimensional seismic wave.Through carrying out fine reservoir description, the internal actual reservoir condition ofLianhua oil layer in Gao21block was figured out. And the suggestions about how to find thereservoirs of high grade and utilize multilateral horizontal well technology to conductdevelopment were put forward, which produced scientific basis for further development.The study results have been applied to field, which acquired good results.14horizontalwells were deployed in the development project, until now5wells have been drilled andputted into production. The average length of horizontal section of the drilled wells is276m,the rate of encountering oil layer is100%. Through production in field, a horizontal well canobtain1.5-2times the productivity of a vertical well, yet a multilateral horizontal well is2.5-3times. And its steady production period is longer, as well as the average of the initialproduction rate of a single well is17.2t/d. The block development index has been obviouslyimproved, where production rate increased from27t/d to55.7t/d, oil recovery rate from0.2%to0.41%and recovery ratio is expected to be raised10percent. Production rate could reach120t/d after all horizontal wells were implemented, which means that the block could beefficiently developed, making the reservoir which was on the verge of abandonment glowingwith new youth.