Various embodiments provide methods and systems for providing fluid lighteners for use in downhole wells. The fluid lighteners may include one or more viscosifiers, one or more aphron generators, and a location-specific non-emulsifying surfactant.

A gas extraction assembly includes an agitator gas trap and a nipple apparatus. The nipple apparatus is coupled to a flowline containing a mud mixture. The agitator gas trap is also in communication with the mud mixture. An inline detector is in the nipple apparatus and configured to help separate the mud mixture from a gas. A tube passes between the nipple apparatus and the agitator gas trap to transport the gas from the inline detector to a gas detection and logging unit for sample recording.

Systems, methods, and computer readable media for the determination of hydrogen sulfide (H.sub.2S) concentration and distribution in carbonate reservoirs using a mechanical earth model. Hydrogen sulfide (H2S) concentration in a carbonate reservoir n may be measured and correlated with horizontal maximum stresses of stress ratios determined using mechanical earth model for a strike-slip fault regime. The hydrogen sulfide (H2S) concentration at different depths in the carbonate reservoir may be determined using the correlation.

Systems and methods for performing a contamination estimation of a downhole sample including at least a formation fluid and a filtrate are provided. A plurality of downhole signals are obtained from the downhole sample and one or more of the signals are conditioned. At least two of the conditioned signals or downhole signals are fused into a multivariate dataset. A principle component analysis (PCA) is performed on the fused multivariate dataset to determine optical and density properties of the formation fluid. Based on at least the PCA, optical and density properties of the filtrate are determined. From the optical and density properties of the formation fluid and of the filtrate, a multivariate calculation is performed to generate concentration profiles of the formation fluid and the filtrate.

Systems, devices, and techniques for determining downhole fluid contamination are disclosed. In one or more embodiments, phase-related properties are measured for a reservoir fluid having a determined composition. An equation-of-state (EOS) is selected and/or tuned based, at least in part, on the measured phase-related properties and the tuned EOS is applied to estimate fluid property values for a reference fluid over specified ranges of at least two thermodynamic properties. Contaminant reference data are generated that correlate the estimated fluid property values for the reference fluid with respective contaminant levels. Within a wellbore, a fluid sample is analyzed to determine a fluid property value. A contaminant level is identified that corresponds within the contaminant reference data to the determined fluid property value of the fluid sample.

A fluid extraction tool can include a body, a sealing pad extending from a portion of the elongated body, a container holding a selective permeability agent (SPA), and a device. The sealing pad can have an opening for establishing fluidic communication between an earth formation and the elongated body, an outer surface to hydraulically seal a region along an inner surface of a wellbore and a recess within the sealing pad establishing a fluid flow channel along the inner surface of the wellbore. The device can inject the SPA through an outlet of the body into the earth formation, and extract a formation fluid through the opening, wherein the formation fluid being collected is from the region along the inner surface of the wellbore sealed off by the sealing pad.

Disclosed are systems and methods for performing a contamination estimation of a downhole sample comprising at least a formation fluid and/or a filtrate. A plurality of downhole signals are obtained from the downhole sample and one or more of the signals are conditioned. At least two of the conditioned signals or downhole signals are fused into a multivariate dataset. From optical and density properties of the formation fluid and/or of the filtrate, a multivariate calculation is performed to generate concentration profiles of the formation fluid and the filtrate.

A system and method for analyzing a gas in a drilling fluid involves a degasser operable to separate the gas from the drilling fluid. A gas analyzer in fluid communication with the degasser receives a sample of the separated gas and determines a property of the gas. A controller in communication with the gas analyzer automates the operation of the gas analyzer by adjusting a parameter of the separated gas sample as the gas sample is supplied to the gas analyzer.

A method for performing a drill stem test (DST) is disclosed. The method includes performing underbalanced drilling (UBD) of exploration wells to penetrate a target interval in a subterranean formation, where UBD is performed when a wellbore fluid pressure is less than a formation fluid pressure to allow a fluid flow from the target interval to surface during a drilling phase of the UBD, determining, based on the UBD of the exploration wells, a measure of the fluid flow from the target interval to the surface, obtaining, based on the UBD of the exploration wells, open hole logs of the exploration wells, where the open hole logs represent a reservoir property of the target interval, and selectively performing, based at least on the measure of the fluid flow and the open hole logs, the DST of the exploration wells.

Drilling fluid can be monitored throughout a drill site and at various stages of drilling operations. The drilling fluid may be analyzed to identify components that make the drilling fluid as well as the volume of each of the components, The volume of each component can be used, for example, to determine a percentage of water in a water-based drilling fluid and the average specific gravity of the water-based drilling fluid without further decomposition of the drilling fluid. The percentage of water and the average specific gravity can then be used to modify the drilling fluid, in real-time, based on conditions in the wellbore.