Measurement of formation porosity and lithology in azimuthal quadrants around the borehole is now available. This new information is provided by a nuclear tool that makes azimuthal density, photoelectric factor and neutron porosity measurements while drilling. In addition, an ultrasonic sensor provides a tool standoff measurement in each quadrant. While rotating, the quadrants are defined by a magnetometer and oriented with the gravity vector, so that bottom, left, right and top quadrants are identitled.The tool Cim be run with several different stabilizer sizes or without a stabilizer, giving the driller more latitude in configuring the bottomhole assembly. The azimuthal capability allows the measurement of porosity with an unstabilized or "slick" tool without degradation of the measurement. This is accomplished by computing the porosity from the bottom quadrant where there is little tool st,mdoff in deviated or horizontal wells. Utilizing bottom quadrant porosities also results in improved measurement accuracy in cases where borehole conditions are poor due to enlargement or washouts. When the tool is stabilized, the quadrant porosity and lithology measurements result in improved geosteering as well as providing a quantitative measure of formation heterogeneity. At bed boundaries, comparison of top and bottom logs in real time results in better bed boundary detection and confirmation of the tool location within the pay zone. When the tool is between boundaries. an beterogeneity indicator can be computed from the quadnmt density, lithology and neutron porosity logs to better evaluate complex formations.The measurement of tool standoff per quadrant provides information on borehole size, shape and rugosity. The data can be used to indicate borehole stability on subsequent bit trips.The paper describes the method of the measurement. h,u'd- 137ware implementation and log examples illustrating the tool features.

No abstract

This paper was selected for pre~entation by an S~E programlcom~'tt~e 0 OWI~g r~v~~~j~ct to correction by the author(s). The material, as presented, does not necessarily ref!ect as presented, have not been reVIewed by th.e SocIety of 'petro eum nglneers an ar t d at SPE meetin s are subject to publication review by Editorial Committees of the SocIety any position of the Society of 'pe~roleum En~,"eer~, Its offIcers, or me~bers. pap~rs p;:sn~s III strations m~y not be copied. The abstract should contain conspicuous acknowledgment of Petroleum Engineers. Permlsslon.to copy IS restrlct?d to.an abstraSctpo E npotomo~e t :3836w~ichar~son TX 75083-3836 U.S.A. Telex, 730989 SPEDAL. of where and by whom the paper IS presented. Write Librarian, , . . o x , , ABSTRACTA new approach, loading a logging source down through the center of a measurement-while-drilling (MWD) collar, offers features that address both radiation safety and environmental issues. This technique reduces crew exposure, allows for safe and timely procedures on the rig floor, and enables fishing of the sources should the bottomhole assembly (BRA) have to be abandoned. After the sources are fished, actions to recover the BRA, abandon the BRA or sidetrack the well are not restricted by the presence of these logging sources.The new source handling approach includes:-A fishable dual source assembly. The gamma ray source and the neutron source are mechanically linked together. This permits them to be simultaneously loaded, unloaded or fished if the BRA becomes stuck.-An integrated collar/shield design. The dual source assembly is loaded directly through its transport shield into the drill collar. At no time is the source unshielded on the rig floor. This reduces the total source loading time and minimizes crew exposure, resulting in a safe and timely operation.-Auxiliary safety equipment.In the event that a source cannot be unloaded after the job is finished, collar shields are clamped into place for safe handling and transport of the collar.References and definitions* at end of paper Illustrations at end of paper 553 -Source security and integrity. The risk of erosion due to mud flow against the source receptacle is quantified. Tests conducted show no erosion problems at rated flow rates with up to 3 % fracture sand by volume in the mud.The system has been tested extensively in the laboratory and in the field for both fishability and erosion resistance, and has proven to an efficient and reliable approach.