Three methods for mitigating airwaves in shallow water marine controlled-source electromagnetic data

Geophysics ◽  
2011 ◽  
Vol 76 (2) ◽  
pp. F89-F99 ◽  
Author(s):  
Jiuping Chen ◽  
David L. Alumbaugh
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Oil And Gas ◽  
Data Set ◽  
Oil And Gas Exploration ◽  
Controlled Source ◽  
Lateral Wave ◽  
Electromagnetic Data ◽  
Stripping Method ◽  
Resistivity Model

In the past several years, marine controlled-source electromagnetic (MCSEM) techniques have been applied successfully in deep water (depth > 1 km) for oil and gas exploration. The application of this technology in shallow water is challenged, however, because of “airwaves” that mask the signal from the target reservoir at depth. Based upon the understanding that an airwave is a lateral wave, which can be analytically expressed in a dual-half-space resistivity model, we propose three airwave-mitigation approaches to reduce the effects of these airwaves on MCSEM data. In the EM “x-bucking” approach, the effect of the airwaves can be “bucked” out from two measurements by using the analytic expression of the airwave. The frequency derivative (dE/dFreq) approach takes advantages of the unique characteristics of the airwaves in frequency domain, enhancing the reservoir signals while suppressing the airwave. The magnetotelluric (MT) stripping method uses the plane-wave feature of the airwaves and subtraction of the lateral wave electric component, which is obtained from measured marine MT impedance and controlled-source electromagnetics (CSEM) data, to generate a new data set in which the effects of the airwaves are removed substantially. By comparing the detectability, which is defined as the ratio of inline Ex fields between a reservoir model and a corresponding baseline model, for a reservoir target in deep water versus shallow water with a moderate 2D bathymetry, we show that the effects of the airwaves in shallow water can be reduced in the data, leading to greater reservoir detectability. In addition, these approaches have been applied successfully to a real shallow water MCSEM data set in which the detectability to the deeper resistive basement is enhanced.

Tubarão Martelo Field Riser System: Shallow Water Challenging

2015 ◽  
Author(s):  
Elton J. B. Ribeiro ◽  
Zhimin Tan ◽  
Yucheng Hou ◽  
Yanqiu Zhang ◽  
Andre Iwane
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Oil And Gas ◽  
Vertical Motion ◽  
Oil And Gas Industry ◽  
System Configuration ◽  
Wave Load ◽  
Gas Industry ◽  
Campos Basin ◽  
Water Problem

Currently the oil and gas industry is focusing on challenging deep water projects, particularly in Campos Basin located coast off Brazil. However, there are a lot of prolific reservoirs located in shallow water, which need to be developed and they are located in area very far from the coast, where there aren’t pipelines facilities to export oil production, in this case is necessary to use a floating production unit able to storage produced oil, such as a FPSO. So, the riser system configuration should be able to absorb FPSO’s dynamic response due to wave load and avoid damage at touch down zone, in this case is recommended to use compliant riser configuration, such as Lazy Wave, Tethered Wave or Lazy S. In addition to, the proposed FPSO for Tubarão Martelo development is a type VLCC (Very Large Crude Carrier) using external turret moored system, which cause large vertical motion at riser connection and it presents large static offset. Also are expected to install 26 risers and umbilicals hanging off on the turret, this large number of risers and umbilicals has driven the main concerns to clashing and clearance requirement since Lazy-S configuration was adopted. In this paper, some numerical model details and recommendations will be presented, which became a feasible challenging risers system in shallow water. For instance, to solve clashing problem it is strictly recommended for modeling MWA (Mid Water Arch) gutter and bend stiffener at top I-tube interface, this recommendation doesn’t matter in deep water, but for shallow water problem is very important. Also is important to use ballast modules in order to solve clashing problems.

scholarly journals Institutions and the Location of Oil Exploration

2019 ◽  
Vol 18 (3) ◽  
pp. 1321-1350 ◽  
Author(s):  
James Cust ◽  
Torfinn Harding
Keyword(s):  
Oil And Gas ◽  
Institutional Quality ◽  
Regression Discontinuity Design ◽  
Host Countries ◽  
Data Set ◽  
Oil And Gas Exploration ◽  
Oil Companies ◽  
Exploration Drilling ◽  
Oil Sector ◽  
Global Data

AbstractWe provide evidence that institutions have a strong influence over where oil and gas exploration takes place. We utilise a global data set on the location of exploration wells and national borders. This allows for a regression discontinuity design with the identifying assumption that the position of borders was determined independently of geology. In order to break potential simultaneity between borders, institutions, and activities in the oil sector, we focus on drilling that occurred after the formation of borders and institutions. Our sample covers 88 countries over the 1966–2010 period. At borders, we estimate more than twice as much drilling on the side with better institutional quality. Subsample analyses reveal effects of institutions on exploration drilling in both developing and high income countries, as well as across three types of operating companies. We find that the supermajor international oil companies are particularly sensitive to institutional quality in developing countries. Our findings are consistent with the view that institutions shape both exploration companies’ incentives to invest in drilling and host countries’ supply of drilling opportunities.

Fundamental Engineering Characteristics of Cohesive Sediments in the Northern Region of South China Sea

2019 ◽  
Author(s):  
Shuzhao Li ◽  
Xu Jia ◽  
Zhigang Li ◽  
Jiagang Li
Keyword(s):  
South China Sea ◽  
Shallow Water ◽  
South China ◽  
Deep Water ◽  
Oil And Gas ◽  
Cohesive Soil ◽  
Northern Region ◽  
China Sea ◽  
Engineering Characteristics ◽  
Offshore Oil And Gas

Abstract The northern region of South China Sea is the important strategic region for the offshore oil and gas resources development in China. The main shallow sediment of the region is the cohesive soil with diverse engineering characteristics difficult to be determined. The paper collects the comprehensive geotechnical data obtained from the laboratory test and the in-situ Cone Penetration Test (CPT) for the offshore oil and gas projects in the northern region of South China Sea, and presents the fundamental engineering characteristics of the cohesive soil. Results indicate that the cohesive soil with the low plasticity index and the low clay particle content in shallow water is obviously different from that in deep water in the northern region of South China Sea. The physical properties of the clay soil with the high plasticity index and high clay particle content in the northern deep water region of South China Sea are similar to those found in the Gulf of Mexico and West Africa. Moreover, there are two different deposit modes for the sediment in the northern region of South China Sea, which are the fine-grained and coarse-grained govern deposit modes in deep and shallow water respectively. It is found that the sleeve friction ratio of the cohesive sediment is very low in shallow water. The normalized values of the clay soil in deep water are consistent with those from the Gulf of Mexico and West Africa.

Automatic, geologic layer-constrained well-seismic tie through blocked dynamic warping

2017 ◽  
Vol 5 (3) ◽  
pp. SJ81-SJ90 ◽  
Author(s):  
Kainan Wang ◽  
Jesse Lomask ◽  
Felix Segovia
Keyword(s):  
Seismic Data ◽  
Oil And Gas ◽  
Synthetic Data ◽  
Optimal Solution ◽  
Velocity Model ◽  
Data Set ◽  
Oil And Gas Exploration ◽  
Interval Velocity ◽  
Velocity Changes ◽  
Dynamic Warping

Well-log-to-seismic tying is a key step in many interpretation workflows for oil and gas exploration. Synthetic seismic traces from the wells are often manually tied to seismic data; this process can be very time consuming and, in some cases, inaccurate. Automatic methods, such as dynamic time warping (DTW), can match synthetic traces to seismic data. Although these methods are extremely fast, they tend to create interval velocities that are not geologically realistic. We have described the modification of DTW to create a blocked dynamic warping (BDW) method. BDW generates an automatic, optimal well tie that honors geologically consistent velocity constraints. Consequently, it results in updated velocities that are more realistic than other methods. BDW constrains the updated velocity to be constant or linearly variable inside each geologic layer. With an optimal correlation between synthetic seismograms and surface seismic data, this algorithm returns an automatically updated time-depth curve and an updated interval velocity model that still retains the original geologic velocity boundaries. In other words, the algorithm finds the optimal solution for tying the synthetic to the seismic data while restricting the interval velocity changes to coincide with the initial input blocking. We have determined the application of the BDW technique on a synthetic data example and field data set.

Risk Assessment of Subsea X-Tree System

2011 ◽  
Vol 148-149 ◽  
pp. 1000-1006 ◽  
Author(s):  
Chang Yong Wang ◽  
Hong Huan Zhang ◽  
Meng Lan Duan
Keyword(s):  
Risk Assessment ◽  
Risk Analysis ◽  
Reliability Analysis ◽  
Deep Water ◽  
Production System ◽  
Oil And Gas ◽  
Oil And Gas Exploration ◽  
Analysis Process ◽  
Subsea Production System ◽  
Exploration And Development

That the oil and gas exploration and development is extending into deep water proceeds the rapidly shift to subsea production system. However, complex subsea equipment and frequency offshore accidents aroused the concern on the risk assessment of subsea system. The paper illustrates the hazard aspects which should be focused on in the subsea equipment compared with the surface equipment. The hazards identification and risk analysis on subsea X-tree system is carried out. A general risk-prevent process of subsea X-tree system is illustrated, so does the reliability analysis process. Besides, some commendations on subsea detection and maintenance are presented in the paper.

The Maximum-Allowable Well Depth While Performing Ultra-Extended-Reach Drilling From Shallow Water to Deepwater Target

SPE Journal ◽  
2017 ◽  
Vol 23 (01) ◽  
pp. 224-236 ◽  
Author(s):  
Xuyue Chen ◽  
Deli Gao
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Oil And Gas ◽  
Pressure Balance ◽  
Gas Reservoirs ◽  
Bottom Hole ◽  
Weight Window ◽  
Oil And Gas Reservoirs ◽  
Well Depth ◽  
Extended Reach Drilling

Summary Ultra-extended-reach wells can be drilled from one platform to develop the remote surrounding satellite oil and gas reservoirs in deepwater. Although the platform is in shallow water, some ultra-extended-reach wells can target the reservoirs in deep water. In ultra-extended-reach drilling from shallow water to deepwater target, some challenges that may be faced are the presence of low temperature, typically weak overburden sediments, unconsolidated formations, and a small sedimentary coverage above the reservoir. This results in a narrow safe-mud-weight window and a limited well depth for ultra-extended-reach drilling operation. In this work, considering the pressure balance of bottom hole including the specific thermal and seepage effects, a method for predicting the well's maximum-allowable measured depth (MD) (MAMD) while performing ultra-extended-reach drilling from shallow water to deepwater target is presented. Meanwhile the factors affecting the MAMD are also investigated. The study shows that seepage significantly affects the MAMD while performing ultra-extended-reach drilling from shallow water to deepwater target: seepage turns out to significantly decrease the MAMD whereas heating the formation is found to be helpful in extending the MAMD. It also shows that the predicted MAMD turns out to be obvious anisotropy; for a normal regime depositional environment, drilling in the direction of minimum horizontal in-situ stress in the formation is prone to attain a wider safe-mud-weight window and a longer MAMD than other directions. Moreover, for a given target zone, the ultra-extended-reach drilling with a horizontal bottom hole has a much longer MAMD than that of ultra-extended-reach drilling with an inclined bottom hole, and the MAMD can also be effectively increased by reducing the annular friction-pressure loss. This work provides a practical tool for enhancing the design of ultra-extended-reach wells to develop the remote satellite oil and gas reservoirs in deep water.

Hedging, Investment Efficiency, and the Role of the Information Environment

2020 ◽  
pp. 0148558X2091633
Author(s):  
Gerald J. Lobo ◽  
Tharindra Ranasinghe ◽  
Lin Yi
Keyword(s):  
Oil And Gas ◽  
Investment Decisions ◽  
Information Environment ◽  
Investment Behavior ◽  
Investment Efficiency ◽  
External Financing ◽  
Data Set ◽  
Oil And Gas Exploration ◽  
Exploration And Production

Extant theories suggest that managers may use hedging either to alleviate underinvestment problems caused by costly external financing or to promote overinvestment by circumventing the scrutiny of external capital markets. We empirically investigate this issue using a hand-collected data set of hedging and investment behavior of oil and gas exploration and production firms. We do not find evidence that hedging alleviates underinvestment problems. However, we do find a strong positive relation between the extent of hedging and the propensity to overinvest. Further analyses indicate that the relation between hedging and overinvesting is stronger in settings where the firms’ information environment is more transparent. A more transparent information environment makes it easier for outside capital providers to distinguish between value-enhancing and value-destroying investment decisions so that greater discretion over internally generated funds becomes more valuable to overinvesting managers. Our study highlights the role of hedging in facilitating overinvestment and the conditions under which this role is likely to be more salient.

Offshore structure design and development

1982 ◽  
Vol 307 (1499) ◽  
pp. 263-277
Keyword(s):  
Deep Water ◽  
Oil And Gas ◽  
Offshore Structures ◽  
Structure Design ◽  
Offshore Structure ◽  
Oil And Gas Exploration ◽  
Exploration And Production ◽  
Offshore Oil And Gas ◽  
Offshore Structure Design ◽  
Offshore Oil

The kinds of technology currently being applied to the design, construction, installation and operation of offshore structures for oil and gas exploration and production are quite sophisticated and include many examples of innovative configurations and approaches. The decade of the 1990s should see further evolution, reinterpretation and improvements of concepts that are already in service or being readied for service. The importance of offshore oil and gas may be judged by the projection that over half of overall exploration investments will go to offshore prospects in future years. This paper surveys some expected evolutions, with particular emphasis on the challenging area of deep-water applications. Some features of a tension leg platform design are discussed as an example of a deep-water oil production system. An attempt is made to recognize the problems of applying advanced engineering and analytical capabilities, when many specialists must interact, to producing a thoroughly engineered design, which is also balanced and economical, for such innovative systems.

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