Resistivity Contrast: The Key to Successful Proactive Geosteering with Induction Type Azimuthal Deep Resistivity Sensor in High Resistivity Formations Conventionally Logged with Laterolog Reactive Tools - A Case Study from Oso Field, Ecuador
Cosios, Gustavo¹; Sierra, Fabricio¹; Teran, Nayda¹; Iza, Alex¹; Sandoval, Juan²; Bustamante, Cesar²; Manrique, Carlos A.³
¹Petroamazonas, Quito, Ecuador.
²Halliburton, Quito, Ecuador.
³Halliburton, Houston, TX.
The challenge presented by Petroamazonas EP at the Oso field was to place a horizontal well in the deepest reservoir of the field, in the cleanest and most permeable portion close to the top of the structure in the Hollin formation. The resistivity values in the reservoir are high and vary between 800 and 1600 ohm-m. To identify quantitative resistivity values is necessary to run a Laterolog type sensor while drilling; this reactive type tool couldn't be optimal for proactive geosteering as its depth of investigation is not enough to identify approaching formation changes and/or geological uncertainties.
To get a proactive geosteering into a desired reservoir is necessary to use an inductive type deep reading azimuthal resistivity tool in combination with other sensors and a real-time forward modeling technique to keep the trajectory all the time at an optimal distance from the top of the reservoir.
With a minimum difference in conductivity of 500 mMhos or more in combination with a strong geosteering solution, is possible to calculate the distance and direction to the forthcoming boundary; these limits were monitored using geosignals which indicate the direction of the most conductive formation; regardless the magnitude, the geosignal can be either positive or negative and helps the reservoir contact specialist to take a trajectory decision. The software uses the geosignal in combination with several resistivity measurements to calculate the distance to bed boundaries.
AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012