Apache positioned the well in a complex reservoir 10-ft [3-m] above the reservoir top without drilling pilot holes. The technology enabled the operator to determine reservoir thickness, fluid contacts, and formation properties for the ideal development strategy. GeopShpere™ reservoir mapping-while-drilling service reduced geological uncertainty in real time using deep resistivity measurements.

• Mapped top of reservoir 33 ft [10 m] deeper than expected, leading to an optimized drilling trajectory to the landing point

• Drilled well without pilot holes, eliminating associated risks and costs

• Determined structure of reservoir top, dip, and base at distances reaching 82 ft [25 m] beyond wellbore

Map reservoir thickness, determine structural dips while landing the well

Apache set a goal of placing a well 10-ft [3-m] TVD above a reservoir sand body in Australia without intersecting it due to geomechanical issues associated with overexposure of the overburden pressure. A secondary objective was to map the reservoir thickness and determine structural dips to to make further decisions about planning the horizontal development section.

The challenges associated with drilling within these reservoir sands included a seismic uncertainty of ±66-ft [±20-m] TVD, a lack of geological markers in the overburden, an unconformity running through the area, and limited nearby offset wells from which to obtain comparison data.

Identify subsurface boundaries to maximize reservoir contact

Apache opted to avoid the risk and cost associated with drilling pilot holes and instead use the GeoSphere mapping-while-drilling service to aid in decision making during landing. Using deep, directional electromagnetic measurements, the GeoSphere service significantly reduces geological uncertainties and mitigates risks associated with entering the reservoir. With a depth of investigation exceeding 100 ft [30m], the service maps a reservoir's position, geometry, and fluid contacts. This information enables operators to make prompt trajectory adjustments to optimize the landing and steering of the wellbore within the reservoir.

Landed well in pay zone, eliminated pilot holes

The GeoSphere service mapped the reservoir, including its top, base, and dip at distances up to 82-ft [25-m] TVD below the well path in real time. It also detected the top of the reservoir 33-ft [10-m] TVD deeper than expected. As a result, Apache maintained the trajectory before geostopping the section 10-ft [3-m] TVD above the reservoir top.

Eliminating pilot holes reduced drilling costs and managed risks while also achieving Apache's goals and objectives in this complex geological environment. The subsurface information recorded by the service during the four landing operations will be used by Apache for further field development.