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Herramienta AIT1The basic references to this set are Anderson and Barber, 1995, and Barber et al., 1999.

Intro to AITTDB 7/01 2Rango de Operacin

Desde 0.1 a 2000 ohmmContraste Rxo< Rt ModeradoRt/Rm< 500 (dimetro de barrena considerado)Dimetro de agujero con moderado Rt/Rm y moderado Rt2The weights are determined for zero conductivity, and skin effect correction is done with fitted functions of the raw R and X signals. The processing for each output is to combine measurements above and below the depth level with weights (deconvolution), then sum over measurements. The weight selection alone determines the output response: shallow, deep, high resolution, low resolution.

Intro to AITTDB 7/01 3Familia AIT SAIT2.5 in. AIT-H/M Platform Express AIT-B/C Primera Herramienta HIT-A500F, 25,000 PSIQAIT3-in., 500F, 30,000 PSI

3Before we get into AIT physics, lets look at all the members of the AIT family of tools. From top to bottom:SAITSlim Access 2.5-in. diameter AIT tool, 25 kHz onlyAIT-HPlatform Express AIT3 5/8 in. dia, 16 ft long, 25 kHz onlyAIT-B/C/DOriginal AIT tool3 5/8-in. dia., 25, 50, 100 kHz AIT-C, AIT-D refer to various telemetry interfaces. Otherwise tools are identical.HIT-AXtreme HPHT tool, 3 7/8 in. dia, 25 kHz, 500F, 25 kPSIQAITSlimXtreme AIT, 3 in. dia., 25 kHz, 500F, 30 KPSI4

ELECTRONICSSECTIONARRAY SECTION4-fin x 2Single 6 or 8-finRepeat same standoff setupon telemetry catridge orHGNS in PExUPPER STANDOFFLOCATIONCOMPENSATORBLOCK SECTION5", 6" or 7" OD fixed StandoffRm/SP Bottom Nose(isolated from mandrel)5'0"1'10"9'2"16' MAKEUPDescripcin AIT Evita que la sonda se colapseFunda de fibra de vidrioCentralizador de TeflnLa nariz tiene el sensor de SP y resistividad del lodo4When we set out to develop a new induction tool, these were the major requirements. In reality, these were not very well set out in the beginning; however, by the time the tool was ready for field tests, these were the chief marketing goals.

There are two primary goals: better resolution in typical boreholes and the ability to determine Rt in complex invasion, including Rxo < Rt. Intro to AITTDB 7/01 5Diseo AIT8 arreglos inductivos (bobinas) con longitudes desde 6 hasta 6 pies.

Profundidades de Investigacin desde el agujero hasta 90dentro de la formacin.

Las curvas del registro es una respuesta balanceada de los 8 arreglos

5All AIT tools contain 8 arrays and the same spacings. The idea of a wide range of spacings is to cover from the borehole to deep in the formation. The original AIT tool was the AIT-B. It was arranged with receiver arrays alternating on each side of the transmitter coil. The purpose of his arrangement was to provide better symmetry in the measurements. It also operated at three frequencies: 25, 50, and 100 kHz. Not all arrays operated at all frequencies: the short arrays operated at 100 kHz, and the longest arrays operated at 25 and 50 kHz. Except for the single-frequency 6-in. and 9-in. arrays, the rest of the arrays operated at two frequencies each. This gives 14 array-frequency combinations, with both R and X signals measured, for a total of 28 channels. Some of the multiple frequencies and attempts at symmetry are a bit of kitchen sink mentality.The next tool was the Platform Express AIT, or AIT-H. The goal was to build a short and light tool, so everything that was not absolutely necessary was eliminated. It operates at a single frequency of 25 kHz, and all the receiver coils are on the same side of the transmitter coil. This provides 16 channels of measurement. Later tools like the SAIT, HIT-A, and QAIT were built with the same array structure and operating frequency.

Intro to AITTDB 7/01 6Concepto del AITLa seal medida es una funcin de 4 variables desconocidas:

Radio del agujero (se obtiene de un Caliper)Conductividad de la formacinConductividad del LodoPosicin de la sonda con respecto a la pared del agujero (Standoff)

El programa OP puede solucionar 2 variables:

Mide directamente la resistividad del lodo y el dimetro del agujero (radio) a travs del caliper de la herramienta Pex6The weights are determined for zero conductivity, and skin effect correction is done with fitted functions of the raw R and X signals. The processing for each output is to combine measurements above and below the depth level with weights (deconvolution), then sum over measurements. The weight selection alone determines the output response: shallow, deep, high resolution, low resolution.

7Correcciones por AgujeroSe asume agujero circularSe solucionan 2 de 4 parmetrosSiempre se soluciona para Rt3 Modos de Correccin:Resistividad del Lodo (Rm) (solo en base agua)**Tamao del AgujeroStand off*

** En lodos Base aceite utilice siempre computar Rm* Precargado en OP para AIT-B/C/D

Si faltan 2, se debe corregir para la menos conocida. Si se tienen los 3 corregir para stand off (por desgaste del mismo)7The most problematic environments for induction tools are borehole, borehole, and borehole. Unlike DIT, the first environmental correction is to correct for the borehole effect. The model is a circular borehole in an infinite homogeneous medium. The parameters of the model are Rm, the formation resistivity Rf, hole radius r, and standoff s. The borehole correction works by using the data from the four shortest arrays to invert for as many borehole parameters as we can at each depth level. The information content of these arrays is such that we can solve for 2 of the 4 parameters in a robust manner. The inversion is done by iterating through a fast forward model to find the parameters that match the 4 array data most closely. The forward model is a data set of over 90,000 points computed with an exact forward model varying all the 4 parameters over their expected ranges. Since the actual formation may be bedded and invaded, the equivalent homogeneous formation always has to be solved for. This leaves one more. This defines the three modes of BHC for AIT: compute Rm, compute hole size, or compute standoff. All except AIT-B/C/D have very accurate built-in Rm sensors. The default for these tools is Compute standoffIn OBM use Compute Rm, especially in holes larger than 9 in.

Intro to AITTDB 7/01 8Computacin de Respuesta AIT

8The logs are formed as a weighted sum of raw, borehole corrected array measurements. The weights are determined by defining the desired response in terms of its vertical resolution, depth of investigation, and near-borehole 2D response. The resulting set of equations is overdetermined and is solved by least-squares techniques for the matrix inversion. The weight determining method was developed by Richard Rosthal at SPC.

9Respuestas AIT

Cambiando el balance de la respuesta se obtiene:

3 resoluciones verticales

Cada una de ellas con 5 profundidades de investigacin

9The wellsite logs come in three resolutions1 ft, 2 ft, and 4 ft. The resolution width is defined by the 90% width of the vertical response function. Each resolution has the same 5 depths of investigation: 10, 20, 30, 60, and 90 in. These 5 logs distill the radial information content of the raw array measurements.

Intro to AITTDB 7/01 10Limites de Diseo AIT

Limites para cada resolucin depender de la relacin entre la Resistividad de la Formacin y la resistividad del lodo (Rt/Rm)AIT diseada para formaciones de alta resistividad y para resistividades pequeas considerar sus limites, para resistividades pequeas considerar HRLT10These sensitivities are summarized in this chart. Before every AIT job the expected parameters should be plotted on this chart to see which resolution is best for the conditions. The red hatched area is Laterolog country!

11Recomendaciones para Seleccionar la Resolucin1-ft para Rt/Rm < 100, agujero en buenas condiciones

2-ft para Rt/Rm < 300, agujero normal

4-ft para Rt/Rm < 1000, agujero en malas condiciones o cuando se presenta el contraste, Rxo < Rt11The 3 resolutions are available because of the necessary tradeoff of resolution and borehole sensitivity. The 1-ft logs are quite sensitive to bad hole conditions. The 2-ft logs are similar in robustness to the ILD logs. The 4-ft logs are industrial strength for really bad hole conditions. 12Recomendaciones para Seleccionar el Modo de OperacinAgujero Normal:Mida el Agujero con el CaliperMida la resistividad del Lodo (Sensor de Fondo)Seleccione Compute Standoff

Agujero Irregular , con herramienta AIT-C o Lodo Base Aceite Mida el Agujero con el Caliper Mida la distancia de la aleta de goma del centralizador (standoff) Seleccione Compute Mud Resistivity12The 3 resolutions are available because of the necessary tradeoff of resolution and borehole sensitivity. The 1-ft logs are quite sensitive to bad hole conditions. The 2-ft logs are similar in robustness to the ILD logs. The 4-ft logs are industrial strength for really bad hole conditions. Ejemplos de Respuestas AIT13The principles of the previous plot are incorporated in the AIT job planner, a Java-based application. It takes expected values of Rt, Rm, and hole size, makes recommendations on rig-up, and plots the results on the graph of the previous slide.

Intro to AITTDB 7/01 145 profundidades de investigacin muestran claramente los perfiles de invasin Rxo > Rt y Rxo < Rt

Diseado para Lodos base Aceite

14This slide shows the Gulf Coast example. The logs separate in the invaded zone in a well-defined manner, and can be inverted for invasion parameters even if OBM is used. In the oil zone, the logs clearly show the Rxo < Rt invasion profile.

Intro to AITTDB 7/01 15Alto contraste entre formaciones sin efectos de capa adyacente.

15The field logs handle high contrast formations with high resolution and no shoulder effect.Intro to AITTDB 7/01 16Inversin de la tendencia de las curvas de 60-90 indican la presencia de anillo de invasin

16The logs indicate the presence of annulus by changing the order of the logs. Here, the 90-in. log reads higher than the 60-in. log.

Intro to AITTDB 7/01 17Segundo ejemplo de anillo de invasin

17This log from Oklahoma shows an annulus profile. The places where the 60 and 90-in. logs are reversed is highlighted in yellow. The zone is an oil zone. The upper, lower resistivity zone where there is still an annulus profile, is a depleted gas zone.