These measurements are relatively inexpensive, although they require a more sophisticated surface system than is needed for directional measurements. Log plotting requires a depth-tracking system and additional surface computer hardware. Applications have been made in both reconnaissance mode, where qualitative readings are used to locate a casing or coring point, and evaluation mode. The main differences between MWD and wireline gamma ray curves are caused by spectral biasing of the formation gamma rays and logging speeds. When this method is used, the wellbore (which is generally inclined) is divided into multiple segments (often 4, 8, or 16). Incoming gamma counts are placed into one of the bins.
Uncertainties in the drilling process result in safety factors or safety margins sufficient to minimize risks in the drilling process. These safety margins represent inefficiencies in the system. This paper will discuss a method for reducing uncertainty as it relates to well bore pressures and hole cleaning to eliminate or reduce these inefficiencies, quantify the rates of penetration that can be achieved, and illustrate the expected wellbore pressures generated by these rates of penetration.
When data is collected manually, the nuances of fluid changes are lost between property measurements. This paper will illustrate the difference between calculating equivalent circulating densities (ECD) with manually collected mud report data and fluid properties collected in real time and the impact that this can have on optimizing the rate at which the operator can drill and trip pipe.
A patent-based methodology will be presented, in which real-time drilling and fluids data are captured and utilized to model ECD pressure data related to the bore hole. The actual and modeled data are statistically analysed to infer information about how rapid a rate of penetration (ROP) may safely be employed to optimize drilling results.
Data will be presented demonstrating the impact that small improvements in fluid parameters and drilling operations can have over the course of drilling a well.
The role that a real-time hydraulics software model plays in providing predictive analytics for ROP optimization will also be discussed. Predictive analytics enable operators to look several stands ahead of the bit to determine if the ROP drilled will cause issues in the future. This enables the identification of the maximum ROP that can be drilled versus optimizing instantaneous ROP. This enables operators to optimize casing-to-casing time.
Summary The phase behavior of the heavy oil (12 wt.%) mixed with hydrocarbon solvent (88 wt.%) has been investigated experimentally via in-situ P-wave velocity and density measurement, density measurement of gas-exhausted oil, and phase behavior observation. Suspended asphaltenes are hardly identified by velocity and density measurement, but their deposition and solidification have been observed at a typical in-situ condition, 22 C and 5 MPa.
Managed Pressure Drilling (MPD) allows one to drill through formations with narrow pressure windows, thereby making those formations that cannot be drilled with conventional techniques accessible. It also provides the capability for early detection and safer handling of well control events. This technique requires accurate estimation of the annular pressure profile and the delta mass flow rate. These measurements can be improved through accurate density and mass flow rate measurement at the high pressure (7500 psi) input side of the well. Since no good metering technologies exist to make these measurements, the objective was to develop a high pressure density and mass flow rate sensor.
A comprehensive review of all existing flow rate and density measurement instruments suggested that an X-ray based sensor was the best option for the high pressure fluid line. Multiple experiments were conducted to determine the electrical power range (voltage and power) for the X-ray tube that would work best for mud between densities in the range of 8 to 20 ppg. Experiments were then conducted to test the accuracy and feasibility of techniques developed for density and volumetric flow rate measurement. Based on these experiments, an X-ray source and detector were identified and a sensor was designed for inline use on 4 inch pipes. Two approaches were developed to estimate density using the sensor. The first was an empirical approach where sensor gray level values were directly mapped onto mud density values though in laboratory experiments. These mappings can then be used in the field to estimate density. The second was a model-based approach that estimates density based on the Beer Lambert's law. Both these approaches were tested experimentally using drilling muds of different densities and compositions.
A mechanism that uses X-rays to determine volumetric flow rate was also designed and tested using both simulations and experiments. A real-time calibration subsystem had to be added to the sensor to preserve measurement accuracy and precision over time. Based on encouraging results from simulations and experiments, a laboratory prototype was built and is currently undergoing flow loop tests. This is the first time an X-ray mass flow rate measurement sensor has been designed to be used on high pressure lines. Preliminary findings indicate that no existing sensors used for similar applications can match the measurement accuracy and frequency that may be offered by this technology. Development of this sensor would improve the safe drilling of complex wells with narrow drilling windows.
Pulsed-neutron logging has evolved over the last 50 years, but the intrinsic physical measurements have remained unchanged, which means that operators cannot obtain a complete picture of the rock and fluids behind casing with conventional tools. However, advances in tool design and a new fast-neutron cross-section (FNXS) measurement provide for an alternative gas-identification technique. Gas in open holes is typically identified from neutron porosity and gamma-gamma density crossover. In casedhole environments, gamma-gamma density measurements are challenging because of the large casing and cement corrections needed. Previous gas identification in casedhole environments has relied on the formation hydrogen index (HI) or neutron porosity (TPHI) log and sigma.
ABSTRACT: Spatially broad surface deformation was detected over the Leeville underground mining complex, which includes dewatered stoping operations of Carlin-style hydrothermal gold deposits in northeast Nevada. Geologic, groundwater, and extraction data were reviewed to form hypotheses of the causes and controls of the deformation, which were poorly understood. It was hypothesized that the hydrothermally altered materials hosting the orebodies form controls on ground behavior because they affect the mechanical properties of the rock mass. To investigate this hypothesis, 3-D material domains of altered and unaltered materials were needed. Because no dataset on alteration intensity was available covering the entire project area, multiple datasets were utilized, including data mining of the drill dataset to produce consistent alteration intensity rankings, density measurements, density interpreted from gravity surveys, and geologic interpretations. These datasets were used to delineate regions of the rock mass with styles of alteration that result in weaker and less stiff materials, and these 3-D geometries were subsequently used to designate material domains in a numerical model. This case study demonstrates a methodology for amalgamating multiple datasets to increase data coverage and improve confidence in the spatial modeling of geomechanical domains. The methods developed here would likely have application at nearby sites and in areas with similar geologic conditions for numerical model geometry-building.
Surface deformation can be produced by both underground mining or groundwater extraction, and subsurface geology can form controls on its expression in multiple ways. The mechanical properties of intact rock are generally a function of lithology and subsequent alteration processes, and consequently these factors can influence ground behavior when a rock mass is subjected to mining or groundwater pumping.
A broad, irregular shaped deformation pattern was identified by InSAR methods in the region overlying the Leeville underground mining complex, which includes extraction of multiple Carlin-style sediment-hosted gold deposits using longhole stoping with backfill and cut and fill mining methods. Cumulative InSAR displacements measured between 2004-2010 are shown in Fig. 1.
In the current market, operational geology and geoscience asset teams have clear and aggressive financial reduction targets that need to be met without compromising the formation evaluation (FE) requirements of a well construction project. Advances in drilling and completion technologies and practices for deep-water wells commonly require operators to drill larger borehole sizes throughout the well construction process. For deep-water subsalt wellbores, this often implies exiting a thick salt layer with borehole deviation in borehole sizes ranging from 14.5 to 17.5 in.
This paper introduces a unique 9.5-in. nominal collar size logging-while-drilling (LWD) density tool that makes it possible to address the FE challenges encountered in large borehole sizes. Any LWD method that can provide crucial cost-effective and accurate FE data can add value to well drilling and logging programs.
The new tool provides density and photoelectric measurements in large-diameter boreholes. It also contains an ultrasonic sensor that can provide accurate borehole geometry information, which is useful for identifying stress-related breakout and providing accurate estimates of borehole volume for later placement of cement for zonal isolation.
In such settings, formation density measurements are crucial for determining key evaluation parameters, such as porosity and rock mechanical properties, but acquisition of these measurements can be challenging using existing LWD technologies. In addition, real-time structural dip information for subsalt environments provides insight for the interpretation of the geological structure of the field but is often difficult to obtain in large-diameter boreholes.
Several case studies demonstrate the value added by the new tool and its breadth of application, as well as the implications for pre-job analysis, bottom-hole assembly (BHA) modeling, data-acquisition procedures, sensor response analysis, and economic benefits to the operator.
The capability of acquiring logging data for interpretation purposes and to fulfill specific regulatory requirements without negatively affecting the drilling program provides a desirable cost-management opportunity.
The results presented here provide a reference for appropriate business cases to help justify the use of this unique LWD technology in drilling and logging projects involving large-diameter boreholes.
A densitometer is used for quantitative density determinations of fluids being produced from core samples during flooding experiments at reservoir conditions. The densitometer is situated in the flowline immediately after the core holder, and measures the density of all fluids being produced from the core sample at the actual pressure/ temperature (P/T) conditions of the flooding experiment. In addition, the densitometer provides timing information about dynamic events during the experiment, e.g. water breakthrough or gas breakthrough.
In the case of two-phase experiments, the densitometer may be used for determining the volumes of the two produced phases, if the density of each of the two fluid phases is known; this is the case in many flooding experiments using oil and water. In such cases, the densitometer may provide data for the produced volumes of oil and water that agree reasonably with fluid volumes determined by an acoustic separator. In complex and prolonged flooding experiments, the densitometer volume determinations may provide an independent confirmation of the volume determinations of an acoustic separator or possibly other devices.
During coreflooding experiments at reservoir conditions it is important to keep track of the fluids being produced from the core sample. For this purpose, a densitometer situated in the flowline immediately downstream to the core sample has proved useful. The densitometer (Paar DMA HPM) has been used at GEUS for obtaining precise density measurements of the fluids being produced from core samples at temperatures up to 115°C and fluid pressures up to 420 bar (Olsen, 2011). However, the rating of the device allows use up to 200°C and 1,400 bar.
Reliable estimation of kerogen density is a requirement for dependable well-log-based petrophysical evaluation of organic-rich mudrocks. As kerogen matures, hydrocarbons are generated and the chemical structure of kerogen is transformed, which can lead to measurable variations in kerogen density. Uncertainty in estimates of kerogen density can significantly impact the reliability of well-log interpretation results.
The objectives of this research are (a) to experimentally quantify the density of kerogen isolated from a variety of organic-rich mudrocks with different origins, (b) to investigate the impact of thermal maturity on kerogen density, and (c) to investigate the impact of synthetic maturation on density of kerogen. We used organic-rich mudrock samples from four formations, to cover a wide range in kerogen thermal maturity. We isolated kerogen from these mudrock samples and estimated the density of the naturally and synthetically matured isolated kerogen samples.
The experimental results indicated that the density of kerogen varies significantly among organic-rich mudrocks with different origins. We recorded densities ranging from 1.19 to 1.77 g/cm3 in kerogen samples when the hydrogen index varied from 603 to 48 mg hydrocarbon/g organic carbon. We also observed that kerogen density increases as a function of thermal maturity. Sensitivity analysis confirmed a measurable impact of kerogen density on estimates of petrophysical properties, such as porosity and water saturation in organic-rich mudrocks. The documented experimental results and procedures can be used to enhance petrophysical evaluation of organic-rich mudrocks, by taking into account the impact of kerogen thermal maturity in the models used for interpretation of core or well-log measurements.
Kerogen disseminated in organic-rich mudrocks presents challenges when performing well-log-based petrophysical evaluation. One such challenge is the lack of reliable estimates of kerogen density in organic-rich mudrocks. Inaccuracies in estimates of kerogen density can negatively influence assessments of porosity, mineralogy, and water saturation in organic-rich mudrocks.
Ability to identify casing collars in real-time is critically important for whipstock casing exit operations, because milling through casing collars could cause significant loss in rig time, excessive damage and even failure of downhole equipment, and potential blockage of the exit window by casing collar spinning. Running wireline to identify casing collars is the typical solution to address the challenge, but incurs additional rig time and cost. This paper present a new technology to locate casing collars in real time with Gamma Ray density measurement, deployed on drill pipe, eliminating the need for a dedicated wireline run. Multiple case histories of field testing the technology in North Sea, covering a wide range of casing sizes from 7-in and 18 5/8-in, are presented as well.
The Gamma Ray density measurement is used for identifying casing collars by detecting the differences in density readings between collar and casing. Gamma rays are continuously emitted from a nuclear source as the density tool moves in the wellbore, and the readings of the near and far detectors, after signal travels through and interacts with casing and formation, are interpreted to calculate density. Density readings are transmitted to surface in real-time through mud-pulse telemetry and are processed to visualize casing collar locations in a log.
The new technology was successfully field tested in North Sea in multiple wells covering a wide range of casing sizes, from 7-in up to 18 5/8-in, with different depths and inclinations. The operational processes and results from the field tests are discussed in this paper. The casing collars were successfully located in each field test, proving the robustness of the technology over a broad range of application parameters. It was discovered from the field tests that the bottomhole assembly (BHA) configuration, tool orientation, tool string rotational speed, sensor standoff and logging speed are critical to clearly identifying casing collars.
This paper presents a new method of using the drill pipe deployed Gamma Ray density measurement to detect casing collars in real-time to optimize whipstock placement for improved reliability and efficiency of casing exit operations. It also provides the best practices of applying the technology in a wide range of well and casing configurations.