Study On Evaluation Methods Of Wireline Formation Test Data In Offshore Low Porosity And Permeability Reservoirs

With development of the offshore oil and gas exploration, low permeability reservoirs have become the main objective of offshore exploration. Compared with the DST, wireline formation testor has the advantages of low cost and relatively high success rate, it has a good prospect in evaluation of offshore low permeability reservoirs. When testing the offshore low permeability reservoirs, wireline formation testor has the problem that pressure recovery is unstable. Based on the study of the current permeability models for wireline formation test data, the dropdown pressure permeability model is improved with introducing the integration method, and a new interpretation model for the dropdown pressure permeability is proposed. For the wireline formation test data of many wells in the three offshore areas, permeability of each pressure measurement point is recalculated by the improved interpretation model. Also, compared with the DST, the results show that two kinds of permeability have a good positive relationship, which indicates that the recalculated permeability is reliable. After formation pressure is regressed on every pressure measurement point in DST interval, formation fluid density is calculated. Compared with the DST data, it shows that when the permeability is over 30mD, the results are very close, when the permeability is betweem 3mD and 30mD, some results are very close, and some are very different, when the permeability is under 3mD, the results are very different, which defines that in what condition formation fluid density can be used. Combining conventional data with DST data, the relationship between wireline formation test permeability and productivity index is studied, it shows that a good proportional relationship between the wireline formation test permeability and productivity index exists, and also, the relationship has been estabilished in the area A, the accuracy is relatively high. It can provide an important basis for forecasting productivity of offshore low permeability reservoirs with wireline formation test data.