Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Hasanov, Azar
Abstract A Geohazards assessment for the riserless section is critical in offshore drilling operations, especially in deepwater environments, such as Brazil or Gulf of Mexico as there is no blowout preventer (BOP) being utilized in this section of a well. If there is any occurrence of geohazards issue without control, then it can have negative impact on human safety and the environment. Geohazards prediction and mitigation in the riserless section requires a multidisciplinary approach with specific types of data from seismic (high resolution recommended), site survey data (multibeam, sub bottom profiler, high backscatter, offset well information (mud weight, drilling trouble events) and most importantly, the geological understanding from regional to local scale. This paper presents critical input data and an integrated workflow of how to identify potential geohazards and respective mitigations for planning a deepwater exploration well in Gulf of Mexico. Not only does it provide a perspective view about the geohazards prediction process, but it also shows the actual outcomes from drilling results. We will use a case study well as an example to illustrate the assessment procedure. This well was identified as a challenging well with complex shallow geology in the riserless section. Drilling trouble events were observed in most of the offset wells in the same geological setting with gumbo, tightspots, shallow water flow and shallow gas. High-definition seismic data was recommended and incorporated into shallow subsurface interpretation and geohazards prediction. We derisked the uncertainty of riserless drilling through the shallow section of the prospect area for upcoming wells, and successfully drilled the riserless section despite the challenging shallow geology.
- Geology > Geological Subdiscipline > Geomechanics (0.48)
- Geology > Geological Subdiscipline > Stratigraphy (0.47)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock (0.46)
- Government > Regional Government > North America Government > United States Government (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Well Drilling > Pressure Management (1.00)
- Well Drilling > Drilling Operations (1.00)
- Well Drilling > Drilling Fluids and Materials (1.00)
- (4 more...)
ABSTRACT The effective stress coefficient determines the influence of confining and pore pressures on rock properties. We measured the permeability of the Lockatong mudstone sample as a function of pore and confining pressures. Using our established laboratory protocol for such measurements, we estimate the effective stress coefficient for permeability. We use an initial stress cycle to remove the effects of inelastic deformation and microfractures due to core damage. The permeability values lie between 1.8 µD (in the first stress cycle) and 100 nD. The effective stress coefficient for permeability is found to be greater than one (nk = 1.28) at the lowest differential stress. We observe a strong dependence of effective stress coefficient with differential pressure – effective stress coefficient decreased from 1.28 at 2.5 MPa to 0.65 at 60 MPa. The measured permeabilities obey a simple power law dependence on the calculated effective stress. Presentation Date: Tuesday, October 16, 2018 Start Time: 8:30:00 AM Location: 202A (Anaheim Convention Center) Presentation Type: Oral
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock (0.76)
- North America > United States > Pennsylvania > Newark Basin (0.99)
- North America > United States > New Jersey > Newark Basin (0.99)
ABSTRACT Compressional deformation in fluids and rocks is influenced by similar viscoelastic effects, as in shear case. In this paper we introduce the importance of bulk viscosity and modulus in frequency-dependent response of elastic velocities. We conducted experiments to measure bulk modulus and attenuation of two heavy-oil saturated rock samples by confining pressure cycling method under varying oscillation frequencies (within teleseismic frequency band 0.001 - 1 Hz), and compared these measurements to a more conventional axial stress-strain technique. We plan to extend the frequency range of the pressure cycling apparatus as well as to modify the setup in order to measure frequency-dependent bulk viscosities of viscoelastic fluids. Presentation Date: Thursday, October 20, 2016 Start Time: 8:30:00 AM Location: 150 Presentation Type: ORAL
Summary We demonstrate that the oscillating pore pressure method is suitable for measuring basic set of rock’s poroelastic properties, such as drained bulk modulus, Biot-Willis and Skempton’s coefficients. The oscillating pore pressure method has been initially developed as a method to determine hydraulic properties of rocks (Kranz et al., 1990; Fischer, 1992). We equip our samples with strain gages and subsequently measure deformation, caused by a harmonic pore pressure pulse, propagating through sample’s porous space. By doing so we simultaneously determine poroelastic and hydraulic properties. One of the main goals of the poroelastic measurement is to improve the estimation of the storage capacity from purely hydraulic pore pressure oscillating method. We show that the storage capacity values from the oscillating pore pressure method alone are overestimated by the order of magnitude; measured poroelastic properties for the tested samples are in agreement with literature data. Hence, oscillating pore pressure method is capable of accurately measuring poroelastic properties. Introduction The oscillating pore pressure method for measurements of permeability and storage capacity has been previously presented in details (Kranz et al., 1990; Fischer, 1992; Song and Renner, 2007). It is based on inducing time-harmonic diffusive fluid flow through the porous sample and subsequent measurement of the upstream and downstream pressure signals. The propagated through the specimen pressure sinusoid is always phaselagged and attenuated on the downstream side. Once the amplitude ratio and phase has been calculated, we can solve the diffusivity equation with oscillatory boundary conditions and estimate the permeability and storage capacity of the sample. Although it allows accurate determination of permeability, the estimation of the storage capacity yields large errors, sometimes on the order of several magnitudes (Bernab´e et al., 2006). As mentioned by Bernab´e et al. (2006) the values of the storage capacity are particularly uncertain if the experiment employs large downstream reservoirs. This is usually done in case of high permeability samples (100 mD and higher) in order to achieve measurable phase and amplitude ratio of the two pressure signals. The storage capacity of the sample is a poroelastic constant, responsible for fluid storage in the sample and defined as (Wang, 2000; K¨umpel, 1991):
Although the typical pulse-decay method is generally favorable in case of tight rocks, it has several drawbacks. First, An oscillatory pore pressure method for simultaneous measurements it assumes that the sample has no compressive storage (additional of rock transport properties, such as intrinsic permeability volume of fluid that can be injected to the porosity and specific storage capacity, and summarize a laboratory when it is exposed to the increased pore pressure) (Walder and setup, being developed for these purposes.