ABSTRACT

The main objective of this study was to investigate the use of a new multilayer mapping-while-drilling technology for mature field development to optimize placement and completion of horizontal wells directed towards the flanks of the field with poor stratigraphic control, abrupt lateral changes, and substantial risk of the aquifer presence. Additionally, the contribution of the data acquired by this technology to provide deep understanding of reservoir geology and the precise calculation of well productivity is given.

Geological uncertainties and operational risks are factors that can jeopardize a horizontal drilling campaign if not managed properly. This is true even for mature fields when the need for further development pushes drilling towards the flanks of the field structure. However, the success rate of such wells can be greatly improved with the use of modern multilayer mapping-while-drilling technologies.

The Ecuadorian oil fields are composed mostly of two main reservoirs, Napo: Lower U and Lower T. Typically, these reservoirs are made of three sand bodies that are characterized by abrupt lateral changes of facies and rock properties due to their estuarine nature, even leading to a complete pinchout of the sand bodies. The latest horizontal prospects are placed and navigated in the flanks of the fields with the aim to optimize production; however, those areas present a higher geological uncertainty for horizontal drilling than the center of the structure where better rock quality is found. Hence, these peripheral wells require making fewer errors during geosteering.

One of the limitations associated to the legacy bed boundary mapping technologies is linked to their poor capabilities to detect multiple thin unproductive layers, which, if overlooked, can result in considerable loss in net pay.

A new multilayer mapping-while-drilling service that makes use of deeper resistivity measurements and new deep azimuthal measurements has been implemented in a block of the Ecuadorian Oriente Basin. This system, supported by a new deterministic inversion engine, improves the understanding of the geology drilled by providing a finer resistivity map around the borehole in real time, leading to more proactive geosteering decisions.

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