Mud Flow Dynamics at Gas Seeps (Nirano Salse, Italy)

The Nirano Salse, known since the Roman Times, are one of the most beautiful and scenic mud volcanoes areas of Italy with thousands of visitors every year. In this work, we apply hydrogeological techniques to characterize mud levels in the Salse by means of GPS-RTK positioning and continuous level logging within mud conduits. Our results suggest that different mud levels in mud volcanoes clusters are due to the different gas-liquid ratio in the conduits and not necessarily exclude interconnection at depth, a hypothesis, on the other hand, that seems strengthened by mud level time series correlations. The presence of shallow aquifers at a depth of 5 to 30 m is also supported by our field data. These shallow aquifers may provide a temporary storage for the ascending gas and when fluid pressure in these aquifers exceeds the tensional strength of the sedimentary rock, leakage of fluids to the surface would occur.

A Change Point Detection Approach for Intelligent Real-Time Identification of Lost Circulation Events During Drilling Operations

Lost circulation is a challenging aspect during drilling operations as uncontrolled flow of wellbore fluids into formation can expose rig personnel and environment to risks. Further, the time required to regain the circulation of drilling fluid typically results in unplanned Non-Productive Time (NPT) causing undesired amplified drilling cost. Thus, it is of primary importance to support drilling supervisors with accurate and effective detection tools for safe and economic drilling operations. In this framework, a novel lost circulation intelligent detection system is proposed which relies on the simultaneous identification of decreasing trends in the paddle mud flow-out and standpipe pressure signals, at constant mud flow-in rate. First, mud flow-out and standpipe pressure signals underlie cubic-spline-based smoothing step to remove background noise caused by the measurement instrument and the intrinsic variability of the drilling environment. To identify structural changes in the considered signals, a nonparametric kernel-based change point detection algorithm is employed. Finally, an alarm is raised if flow-out and standpipe pressure decreasing trends have been detected and their negative variations are below prefixed threshold values. The proposed intelligent lost circulation detection system has been verified with respect to historical field data recorded from several Eni wells located in different countries. Results show that the proposed system satisfactorily and reliably detects both partial and total lost circulation events. Further, its integration with already existing Eni NPT prediction models has led to a significant improvement in terms of events correctly triggered.

Sonic Drilling with Use of a Cavitation Hydraulic Vibrator

Sonic drilling is a soil penetration technique that strongly reduces friction on the drill string and drill bit due to liquefaction, inertia effects and a temporary reduction of porosity of the soil. Modern studies to assess the effect of the vibration frequency of the drill bit on the rock fragmentation in experimental and theoretical works on drilling various rocks by the sonic method have shown that vibration frequencies of ~ 1.4 kHz are the most beneficial for ensuring the maximum drilling speed in hard rocks. The above frequencies of excitation of vibrations of the drill bit can be achieved by using a cavitation hydrovibrator. The cavitation hydrovibrator is the Venturi tube of special geometry that converts a stationary fluid (flushing mud) flow into an oscillatory stalling cavitation flow and hydrovibrator structure longitudinal vibrations. The drill bit vibration accelerations are realized in such a drill string, leading to the destruction of rock. Efficient removal of rock particles from the bottomhole is achieved due to high-frequency shock self-oscillations of mud pressure exceeding the steady-state pressure at the generator inlet. The cavitation hydraulic vibrator lacks the main disadvantages of submersible hydraulic hammers.

Helical Flow of Drilling Mud With Cuttings in a Vertical Well

The paper presents the results of an investigation into drilling mud flow with cuttings in a vertical well. The drilling mud rheology was described with the Herschel-Bulkley model. The axial Reynolds number was around 1000, the flow regime changing together with drill pipe RPM. The investigation covered the flow’s structures, integral parameters and cuttings transport in relation to drill pipe RPM and rate of penetration (ROP). In the laminar flow, most of the particles were localized in the quasi-solid region to move together with the last; the integral parameters had little dependence on drill pipe RPM increase. Increasing drill pipe RPM resulted in formation of the Görtler vortices near the channel’s external and internal walls, whose interaction led to the formation of smaller eddies converting the flow into a turbulent one. Due to the turbulence dispersion, the region taken by the particles widened. Particles suppress the vortex intensity near the channel’s external wall. Under the conditions described, increasing drill pipe RPM and ROP resulted in higher pressure drops and lower transport efficiency.

Mud Volcanoes

The eruption of mud and magma can be influenced by earthquakes and reports date back more than 2000 years. Dozens of examples of eruptions have now been documented in response to both static and dynamic stresses from earthquakes. Already erupting systems are most sensitive to earthquakes compared to initiating new eruptions. Multiple plausible mechanisms have been proposed for triggering eruptions including disrupting particle-rich materials, mobilizing bubbles, or changing permeability—changes may occur both within and outside the reservoir hosting the materials that ultimately erupt. Using historical examples of triggered mud eruptions, we explain why it is unlikely that the Sidoarjo mud flow (sometimes nicknamed “Lusi”) was initiated by an earthquake. As multiparameter monitoring of volcanoes expands, it may eventually be possible to identify triggering mechanisms and how seismic waves influence magma and mud mobility in field settings.

ANALISIS KELAYAKAN INVESTASI RELOKASI TOL PORONGGEMPOL AKIBAT TAMBAHAN LINGKUP PEKERJAAN

ABSTRACTSurabaya–Gempol Toll Road is a toll that has operated since 1986, but in 2006 the Porong-Gempol route collapsed due to lapindo mud flow. Therefore, the toll road needs a relocation. On the construction of its relocation, additional scope of work was added and affected the feasibility of the investment which must be put into consideration for analyzing purposes in order to regain the initial feasibility value of 14.84% IRR. The forecast of cost and income analyzed with financial approach. The method used are Net Present Value (NPV) and Internal Rate of Return (IRR) with a discount rate of 11.8%. The result of investment feasibility after additional scope of work shows that the NPV during concession period (39 years) is negative Rp459.150.000.000,00 and IRR at NPV = 0 is 9,55%. To return the feasibility value, concession period is must be increase to 50 years with adjustment of the toll fee to Rp1.625 in 2021 and Rp1.980 in 2023. It shows that NPV is Rp1.037.727.000.000,00 and IRR at NPV = 0 return to 14,84%.Keywords: Additional scope of work; Compensation; Feasibility; RelocationABSTRAKJalan Tol Surabaya-Gempol merupakan jalan tol yang sudah beroperasi sejak tahun 1986 akan tetapi pada tahun 2006 ruas tol Porong-Gempol terputus oleh lumpur lapindo sehingga perlu dilakukan relokasi. Dalam pembangunan relokasi ruas tol tersebut, terjadi tambahan lingkup pekerjaan sehingga membuat biaya investasi membengkak sehingga perlu diketahui pengaruhnya terhadap nilai kelayakan investasi proyek tersebut untuk kemudian dilakukan analisis dalam upaya pengembalian nilai kelayakan yaitu IRR sebesar 14,84% seperti kondisi awal. Prakiraan biaya dan pendapatan akan dianalisis dengan pendekatan finansial. Metode yang digunakan adalah Net Present Value (NPV) dan Internal Rate of Return (IRR) dengan discount rate 11,8%. Hasil evaluasi kelayakan investasi akibat tambahan lingkup pekerjaan menunjukkan bahwa NPV selama masa konsesi (39 tahun) adalah negatif Rp459.150.000.000,00 dan IRR pada NPV = 0 adalah 9,55%, nilai IRR ini lebih kecil dari discount rate yaitu 11,8%. Untuk mengembalikan nilai kelayakan, dilakukan skema kompensasi penambahan masa konsesi menjadi 50 tahun dan penyesuaian tarif tol baru menjadi Rp1.625,00 pada tahun 2021 dan Rp1.980,00 pada tahun 2023. Hasil dari skema kompensasi tersebut menunjukkan bahwa NPV sebesar Rp1.037.727.000.000,00 dan IRR pada NPV = 0 kembali ke nilai 14,84%.Kata kunci: Kelayakan; Kompensasi; Relokasi; Tambah Lingkup

Seagrass Potential as Supporting Ecotourism in Sibu Island, Subdistrict North Oba, North Maluku Province

Seagrass Ecotourism is a tourism activities based on the ecosystem of seagrass. Component of seagrass consist of vegetation and biota that associated with the seagrass. The purpose of this research is to understand the condition biophysics of seagrass (Types of seagrass, Cover of seagrass, fish, makrozoobenthos, types of substrat, water brightness, the depth of the seagrass) and to establish the suitability of seagrass to support nautical ecotourism. This research have been done in Sibu island, Guraping village, north oba district, Tidore city for 6 month from April – September 2020. The method that used is a survey method consist of direct measuring of types seagrass, cover of seagrass, fish, makrozoobenthos, types of substrat, water brightness, the depth of the seagrass. The data analysis includes percentage of cover seagrass and the suitability index of seagrass ecotourism. The result of the biophysical study were obtained are 8 types of seagrass, cover of seagrass (51,04- 92,71%), fish (12 types), makrozoobenthos (17 types), brightness (77-100%), substart (sand, muddy sand, mud) flow speed (0,01- 0,06 m/dt) and the depth of the seagrass (1-2,5 m). Sibu island could be developed as a region of Seagrass Ecotourism with index suitability tourism (IKW) station 1,3,4 and for the whole are located in category S1 (very suitable) and station 2 is in the suitable category.