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Abstract

In order to meet world energy demand, wells have to be drilled in more challenging frontiers and<br>within very thin reservoir beds. Conventional geosteering and LWD measurements face considerable<br>challenges with chasing thin targets. However, geosteering into such thinner reservoirs has been<br>successfully achieved through the application of next generation LWD measurements. Deep, directional<br>resistivity (DDR) from the PeriScope LWD allows well placement to be optimized in real time by using<br>the tool’s sensitivity to approaching bed boundaries and the ability to accurately map distance to such<br>bed boundaries and formation dip. The PeriScope technology has proven its ability to unlock previously<br>uneconomic targets in both clastic and carbonate reservoirs all over the world by providing for<br>proactive well placement.<br>In Saudi Arabia, Aramco has made use of applying the PeriScope LWD and well placement services for<br>its more challenging targets. In this paper a case study is outlined where 2 laterals were drilled into a<br>carbonate reservoir, with and without PeriScope LWD. A comparison is made between results achieved<br>drilling lateral 1, using PeriScope LWD and in lateral 2, drilling using a conventional LWD approach. In<br>both cases the objectives of the well was to place the well 1 ft below the top of an anhydrite cap rock<br>and also to keep the well away from possible water encroachment thereby improving total oil recovery.<br>Conventional geosteering relies on logs from offset wells and real time measurements. An assumption<br>is made that the formation follows a layer-cake model, in which properties are assumed to be laterally<br>continuous. This assumption is often invalid, as smaller scale variations in structure can also<br>significantly impact on geosteering, especially in thinner targets and provides a considerable challenge<br>for conventional geosteering. By using PeriScope these changes can be proactively managed in real<br>time. In this case study lateral 1 was planned and drilled using PeriScope LWD in the BHA while Lateral<br>2 was later drilled with a conventional LWD BHA. Lateral 1 was placed in a porous stratum from target<br>entry (TE) to total depth (TD) with no reservoir exit. Whereas 16.8 % borehole-to-reservoir exposure<br>with formation greater than 0.15 porosity unit was achieved in the lateral drilled with conventional<br>LWD. The results confirm the added value of proactive well placement through the use of the PeriScope<br>LWD technology.

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/content/papers/10.3997/2214-4609-pdb.248.292
2010-03-07
2021-11-28
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