Schlumberger Technology Corporation

Ralf Heidler

Peter Speier

Martin E Poitzsch

Steven F Crary

Bruno Luong

Krishnamurthy Ganesan

Nicholas J Heaton

Cengiz Esmersoy

Henry N Bachman

Charles Woodburn

Jack A La Vigne

Roger A Dworak

A method to determine formation properties using two or more data sets in which the solutions corresponding to the data sets represent shared and distinct formation properties. The method analyzes the data sets and computes distributions for the shared and distinct formation properties from which the formation properties are determined.

Method for analyzing data having shared and distinct properties

A method of reducing ringing artifacts in a nuclear magnetic resonance measurement is provided. The method utilizes a new pulse sequence that offers ringing cancellation opportunities as well as compensation for otherwise accumulating spin dynamics errors. Ringing cancellation is accomplished by forming linear combinations of spin echoes induced as a result of the pulse sequence. Because the linear combinations are formed between closely spaced spin echoes (i.e., echoes within the same sequence), the likelihood that the ringing artifact will have changed between measurements is diminished.

Method for reducing ringing in NMR measurements by combining NMR signals having a spin echo and spurious signal component

A method is provided for gathering information on the pore pressure in an earth formation surrounding a wellbore. The method includes the initial steps of selecting at least one suitable property (e.g., porosity, drilling fluid composition, etc.) of the drilling environment (which is defined by the wellbore and the surrounding formation) and at least one NMR parameter (e.g., T2 distribution) in an NMR measurement response. The method selects a suitable property for which values over a plurality of wellbore depths can be correlated with the characteristics or behavior of the pore pressure in the earth formation. The method further includes conducting an NMR measurement at a plurality of wellbore depths, thereby generating an NMR response from the drilling environment. The measured values of the NMR parameter in the NMR response are then correlated with values of the suitable property. Next, the values of the suitable property are compared over the plurality of depths, and then the correspondence between the property values is correlated with the behavior of the pore pressure over the plurality of depths. In this way, the characteristics of the pore pressure in the earth formation over the plurality of wellbore depths are determined.

Method and apparatus utilizing NMR measurements to gather information on a property of the earth formation surrounding a wellbore

A method for determining an earth formation property from nuclear magnetic resonance measurements includes applying suppression functions to spin echoes in at least one burst measurement set to produce a modified burst data set, the suppression functions to suppress contribution of spin echoes having non-negligible polarization correction; inverting the modified burst data set and at least one standard spin echo measurement set to produce a nuclear magnetic resonance parameter distribution, the at least one standard spin echo measurement set and the at least one burst measurement set being acquired on an earth formation sample; and computing the earth formation property from the nuclear magnetic resonance parameter distribution. The nuclear magnetic resonance parameter includes at least one selected from longitudinal relaxation time, transverse relaxation time, a ratio of longitudinal relaxation time to transverse relaxation time, and diffusion constant.

Method for the inversion of CPMG measurements enhanced by often repeated short wait time measurements

The present invention relates generally to an apparatus and method for obtaining an azimuthally resolved nuclear magnetic resonance measurement of an earth formation traversed by a borehole. The measurement can be made while drilling or using a wireline tool. At least one gradient coil is positioned circumferentially around the tool. A magnetic field is produced by the coil in a region of the formation facing the coil. The magnetic field is substantially parallel to the static magnetic field produced by a pair of permanent magnets which form a part of the tool. The additional field causes an additional phase shift for spins located in the region so that the spins subjected to the additional field do not form a spin-echo.

Nuclear magnetic resonance logging with azimuthal resolution using gradient coils

The present invention is directed to a method for generating a pulse sequence using a logging tool. A pulse programmer is provided for adaptively controlling the creation and application of a sequence of RF magnetic field pulses to an earth formation. In order to control the RF pulses, a portion of a memory device is partitioned into a plurality of tables and control information is stored in the tables. The pulse programmer creates the pulse sequence using information found in the memory device and the operating conditions of the tool. The structure of the partitioned memory device allows the pulse programmer to adapt and change the timing of the pulse sequences autonomously downhole.

Apparatus and method for generating a pulse sequence

The present invention is directed to a nuclear magnetic resonance logging-while-drilling tool. The tool comprises a drill bit, drill string, a plurality of RF antennas, and at least one gradient coil. The tool further comprises a plurality of magnets that are polarized in a direction parallel to the longitudinal axis of the tool but opposite to each other. The configuration of magnets and antennas provides for at least two NMR regions of investigation.

Apparatus and method for obtaining a nuclear magnetic resonance measurement while drilling

There are many natural pauses during rotary drilling operations where a portion of the drill string remains stationary. Pauses include drill pipe connections, circulating time, and fishing operations. These pauses are used to obtain formation evaluation measurements that take a long time or that benefit from a quiet environment, as opposed to the naturally noisy drilling environment. Various techniques that are sensitive to the mud flow, weight-on-bit, or motion of the drill string may be used alone or in combination to identify the drilling mode and control the data acquisition sequence.

Apparatus and method for determining a drilling mode to optimize formation evaluation measurements

The present invention is directed to a method for computing a distribution of spin&mdash;spin relaxation times. The spin-echo amplitudes are obtained by hardware integration of the receiver voltages over a time window. A linear operator is utilized to map a relaxation-time distribution to spin-echoes, produce a singular value decomposition (SVD) of the linear operator, determine vectors of the SVD, and compress the spin-echo data using the vectors. To eliminate a telemetry bottleneck, the T,spectrum is computed downhole and transmitted to the surface.

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Stafford, TX, United States of America

Ralf Heidler