The Application of Enhanced Geo-Navigation Technique in Multilateral Well Targeting Multiple Reservoir Zones in Challenging Geological Environment
Authors: El-Din Ibrahim Hossam , Al Aboud Nour , Odiase Paul , Reyes Jorge 
Published: June 2020

Objective/Scope: Advanced geo-navigation technique in multilateral wells is currently being used to optimize oil production from a number of reservoir zones in Mauddud formation in the ongoing development of Sabriyah oil field. Multilateral wells generally help reduce cost of hydrocarbon production and are known to perform better than single horizontal wells. However, the application of appropriate geo-navigation strategy and downhole logging-while-drilling (LWD) technologies to achieving maximum reservoir exposure is key to production outcomes. Well-ML was planned as a multilateral well with two horizontal drain sections LAT-0 and LAT-1, each targeting multiple reservoir zones MaB, MaC and MaD in Mauddud. The main objectives of the two horizontals was to place the wellbores in the more porous and less dense sections of the targeted reservoir zones, achieving 30 - 45%, 10 -15% and 50 - 60% of reservoir footages in MaB, MaC and MaD respectively. The variation in the reservoir depositional facies and structural uncertainties due to the presence of a major fault pose geosteering challenges, also risking not achieving the require reservoir footages in the targeted Mauddud reservoir zones.

Methods, Procedures, Process: A geo-navigation model was created using offset well gamma ray, resistivity, bulk density and neutron measurements. Petrophysical evaluation of simulated curves from LWD tool responses along the wellbore trajectory was used to optimize the location of the horizontal wells in the targeted reservoir zones. Selection of BHA tool was based on the degree to which simulated curves from specific LWD tools displayed identifiable response to variation in reservoir facies and structural character. The implemented BHA comprised of the rotary steerable system, azimuthal deep resistivity "distance-to-boundary" technology, and the near bit density-porosity.

Results, Observations, Conclusions: The enhanced geo-navigation technique of integrating the near-bit-density-porosity and the azimuthal deep resistivity distance-to-boundary tools played a major role in navigating the wellbore within the sweetest spot of the multiple reservoir zones with confidence. Percentage footage achieved in MaB-MaC-MaD was 49%- 14%-37% in LAT-0 and 34%-17%-49% in LAT-1. The positioning of the density/porosity sensors close to the drill bit reduced the reaction time to mitigate the challenges posed by abrupt changes in reservoir density/porosity characters and allowed for an earlier estimation of reservoir structural dips, particularly in MaC zone where there was poor azimuthal sensitivity in the deep resistivity measurements. The successful and continuous real-time geo-navigation operation resulted in an optimized production outcome that is 3 times the production from single horizontal producer recorded in the same multiple reservoir zones.

Novel/Additive Information: Enhanced geo-navigation technique in multilateral well targeting multiple reservoir zones.