Interpretation of Subsurface Fault Through Multi-Level Second Vertical Derivative Gravitational Data in Bittuang Geothermal Working Area, South Sulawesi, Indonesia

The research was conducted in Bittuang, Tana Toraja Regency, South Sulawesi Province, as one of the geothermal prospect areas and targets for the initial stage of the Government exploration drilling program for the 2020-2024 period. One aspect of geothermal is the manifestation control structure as a fluid migration path from below the surface. Therefore, identification of existing structures in the Bittuang geothermal area was carried out and confirmed the surface geological structure contained in the Bittuang geothermal geological map. In determining the presence of a fault and knowing its characteristics such as the type of fault, the direction of the dip, and the magnitude of the dip of the fault, the gravity data is processed using the multi-level second vertical derivative (ML-SVD) method. To strengthen the interpretation, the results from the ML-SVD were matched with the data from the horizontal gradient (HG) method and the geological data of the structure of the study area. From this process, there are 27 faults in the Bittuang geothermal area, two of which are indicated as controlling faults for the manifestation of the Balla group and the Cepeng group. This research is expected to describe faults in the Bittuang geothermal area, which can support detailed exploration activities.

Exploration Drilling in Remote Areas

In order to meet the country's future energy requirements, and in particular the increased demand for electricity and water in addition to major industrial growth, Bahrain's National Oil and Gas Authority (NOGA) has taken the strategic decision to import Liquefied Natural Gas (LNG) to supplement existing local gas supplies as a long term energy policy. NOGA and the National Oil and Gas Holding Company B.S.C (c) (NH) signed project agreements in 2015 for the development of an LNG Receiving and Regasification Terminal in the Kingdom of Bahrain with an international consortium. The purpose of this paper is to shed light on this ‘first-of-its-kind’ project development in the Kingdom of Bahrain in order to highlight (i) the challenges and management of such challenges, (ii) the ultimate project/operational objectives and successful results, and (iii) lessons learnt.

Application of BigData technology to improve the efficiency of Arctic shelf fields development

Development processes in the Arctic zone require that a set of tasks related to the development or improvement of technologies, as well as to the optimization of project management methods be solved. It has been noted that in order to solve the tasks, fast updated Big Data is needed, the timely acquisition and processing of which will allow for unbiased assessment of the current situation, taking appropriate management decisions, and prompt adjusting as new factors arise. It has been concluded that the introduction of Big Data technology is considered to be the most efficient Industry 4.0 tool for geological survey, and data arrays on the state of exploration of the territories and the results of exploration drilling can serve as the basis for an information model of oil and gas exploration. It has also been found that the array accumulated by subsoil users in the course of scientific research makes it possible to significantly increase the state of exploration of the natural Arctic environment and assess in an unbiased manner the natural processes that occur in the areas of the northern seas. Based on the analysis of the collected data, to predict the state of the natural environment and further develop optimal technical and managerial solutions for the development of the Arctic fields is possible.

Mathematical assessment of the depth of the passive method of induced polarization based on experimental data

The article discusses a numerical model for assessing the depth for the passive method of induced polarization based on previously obtained experimental data at the Samson field (Republic of Khakassia). The model is based on the mathematical model of Komarov, who derived equations for the anomalous polarizability of a sphere observed on the Earth’s day surface, the proposed model for estimating the depth of the anomaly depends on the size of the proposed field and the induced polarization coefficient observed on the surface. In the course of the numerical assessment, it was shown that there is a convergence of data from field observations, exploration drilling and mathematical modeling.

Experience in applying the method of fractal analysis to clarify the boundaries of facies zones when introducing digital technologies in the exploration process

In order to improve the efficiency of exploration drilling at various greenfield license areas owned by Rosneft Oil Company, Tyumen Petroleum Scientific Center LLC has been actively developing and implementing various innovative technologies in recent years that allow increasing the probability of discovering new hydrocarbon deposits. One of such approaches is the use of different methods based on the principles of fractality of geological objects. The article presents the results of using the fractal analysis method to solve one of the applied problems of oil and gas geology, namely, the correction of the boundaries of facies zones on facies maps, which are the basis for constructing risk maps for the "reservoir". It is shown that the boundaries of the facies zones on facies maps, built mainly on seismic data and a limited amount of materials from exploration drilling, have a large variability. The found statistical relationship between the distribution of the total reservoir thicknesses in different facies zones and the fractal dimension of the traps made it possible to correct facies and risk maps.

Geophysical methods help to assess potential groundwater extraction sites

Complex geology in glacial terrain makes groundwater exploration challenging for water supply companies. Abrupt lateral changes of geological conditions, for example, raise the risk of unsuccessful exploration drilling. At some locations, local water supply companies experience a large number of dry wells, raising the need for better exploration approaches. The use of geophysical techniques enables the detection and characterization of subsurface structures in terms of aquifers and aquitards.We present two examples in which seismic and resistivity methods are combined for subsurface characterization. A thrust structure is detected in the Varde study area in Denmark and a channel structure is mapped in the Hamburg-Sülldorf study area in Germany. The different imaging characteristics of seismic P‑ and S‑waves are demonstrated. The combination of seismic and resistivity methods enables delineating groundwater-bearing and groundwater-barrier layers down to a depth of 150 m.

The application of VOI method to shape a strategy of additional exploration

Background. An optimal exploration strategy creates a significant share in value of project on exploration stage. The paper describes an example of solving the following tasks: determining the feasibility of additional exploration drilling; evaluating the value of drilling of one or more exploration wells; determining the optimal placement for exploration wells and drilling order. Authors presenting the modification of VoI (Value of Information) method and its application. Materials and methods. Complex probabilistic models were created summarizing main uncertainties and limitations, both geological, technical and technological. At the first stage three equiprobable geological concepts were made. For each concept probabilistic geological modelling was proceeded and then realizations corresponding to values of reserves P10, P50, and P90 were selected. Further, detailed production forecasts and economic estimates were performed. The analysis used the well pad and the corresponding area for exploration drilling as a unit of calculation. In the article the authors introduced the concept of remaining uncertainty. Application of modified VoI method allowed to form ‘dynamic’ (i.e. depending on exploration wells drilling order) range of areas for additional exploration which provide the best decrease of remaining uncertainty. An additional exploration strategy has been formed, which includes the necessary and sufficient number of wells and their drilling order. A decision tree was created depending on the success or failure of each subsequent exploration well. Results. The use of the modified VoI approach made it possible to achieve the objectives and obtain economical estimates, all of which combined to facilitate the adoption of decisions. As a result, a program for two exploration well drilling was created which would reduce the uncertainty by 90% from its initial value. Conclusions: The adopted VoI method could be applied to fields at the stage of additional exploration as well as to fields at early exploration stage to develop an exploration drilling strategy.

Optimizing Casing Cut and Pull Operations Efficiency Using Ultrasonic Logging Data

Thousands of wells will enter the plug and abandonment (P&A) phase across the Norwegian Continental Shelf (NCS), either for permanent well abandonment or section abandonment with subsequent sidetracks. In the medium and long term, more wells will be added to follow the same path as exploration, drilling, and production continues. The cost of abandonment operations demands improvement of how P&A operations are performed. A critical, and often time-consuming operation, of well or section abandonment is to cut and pull (C&P) some of the casing strings. Uncertainties about the status of the annular contents and the material within it, such as settled solids, contaminated cement, or well geometry might pose restraints that could hinder the C&P efficiency. The uncertainties may cause operations to deviate from the plan, increasing the time and the costs required. New-generation ultrasonic tools, in combination with sonic tools, provide information about the annulus material with a detailed map of the axial and azimuthal variations of the annulus contents. The geometric position of the inner pipe can be determined relative to the outer casing or borehole using advanced measurements. Logging with ultrasonic and sonic tools is a noninvasive method that can increase the efficiency of C&P operations. In this paper we discuss three case studies of wells ranging from 2 to 40 years old. Some of the wells have reached the end of their economic life and are now ready for permanent plug and abandonment (PP&A) or slot recovery. Each case is unique with different casing sizes being retrieved, along with varied annulus contents observed from ultrasonic and sonic log data. The innovative use of the data interpretation with advanced workflows decreased uncertainties about the annulus contents and enabled following an informed C&P strategy. In all three cases, the casing sections were retrieved without difficulties from the recommended depths of the analysis. Casing milling was performed in intervals where C&P was not supported by the data analysis.