Cased-Hole Formation Resistivity (CHFR) Technique Improves Hydrocarbon Saturation Monitoring in Developed Reservoirs

Abstract

TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractThe ability to detect and evaluate bypassed hydrocarbon and track fluid movement in sandstone reservoir is vital in the quest to improve production and increases recovery. The main technique, which has been used for monitoring reservoir saturations, is TDT tool. But, it was hard to interpret the TDT data in the low formation water salinity reservoirs. This SPE 104472Cased-Hole Formation Resistivity (CHFR) Technique Improves Hydrocarbon Saturation Monitoring in Developed Reservoirs G.M. Hamada, KFUPM cases, and that the quick look of CHFR logs always agrees with its quantitative interpretation, which gives the trust to relay on quick look of CHFR log, if a fast decision is required.1. Water saturations derived from CHFR log were more accurate than those from TDT log. Also, CHFR results were very representative to reservoirs of low formation water salinity, low porosity 2. TDT log gives water saturations greater than that given by CHFR log against same intervals. Therefore, Decisions of water shut-off operations based on TDT log, we will loss this difference of oil saturation, which means that large volumes of oil may be lost. Interpretation of CHFR log is easier than that ofTDT log because while interpretation of CHFR log, two factors which come from the same origin, are compared with each others. These two factors are open and cased-hole resistivities, so, it is easy to compare them and detect any differences between them. In the case of TDT log, two different factors are compared with each others; these factors are TDT sigma and open-hole resistivity that makes the comparison difficult and not realistic.4. In case of proper and successful water shut-off operations, the pay-out-time of CHFR log is less than that of TDT log, despite being much more expensive than TDT log. Therefore, if the using of CHFR log is mandatory (due to well conditions), it will be more economic than TDT log.

Tecnicas geoestatisticas aplicadas na modelagem da saturação de oleo

“…Entretanto, um número significativo de reservatórios tem a sua produção mantida por injeção de água, fazendo com que ocorra a redução ou alteração da salinidade da formação, podendo acarretar obtenção de valores incorretos. Outras vantagens a serem consideradas são a sua utilização em poços revestidos; capacidade de distinção entre óleo e gás, diferente dos perfis de resistividade; a leitura não é influenciada pela geometria dos poros; sua maior resolução vertical quando comparadas com as ferramentas de indução permite identificar um maior número de variações na curva de saturação de água (Hamada, 2006).…”

“…Dentre as desvantagens, pode-se citar que em águas com baixa salinidade (inferior a 35.000 ppm), não consegue diferenciar entre óleo e água por que a taxa de captura de nêutrons é semelhante. Também não pode lidar com formações que apresentam valores de salinidade distintos pois, a água injetada pode conter valores de salinidade distintas dos da formação, gerando assim um erro na leitura (Hamada, 2006).…”