Vertical Depth Research Articles

Wellbore cooling and heat energy utilization method for deep shale gas horizontal well drilling

The downhole high-temperature problem has become a bottleneck that restricts the efficient development of deep shale gas resources in China. This study highlights the characteristics of the deep shale gas drilling process to develop a transient model of wellbore temperature distribution for deep shale gas horizontal section drilling through thermal resistance analysis, which is verified using experimental and field data. Based on this model, the influence of the circulation time, drilling fluid flow rate, drill pipe rotation speed, rate of penetration, drilling fluid inlet temperature, and drill pipe thermal conductivity on the wellbore temperature distribution during horizontal well drilling is investigated. The results indicate that an insulated drill pipe is the most effective measure for cooling down the wellbore. Subsequently, a system for wellbore cooling and heat energy utilization while drilling based on insulated drill pipes is established in conjunction with the organic Rankine cycle. The results show that the estimated maximum power generation of this system was 990.120 kW when the bore diameter is 215.9 mm, the design depth of the well is 6095 m, the vertical depth of the well is 4313.76 m, and the inlet temperature is 20 °C.

Degradation Reduces Microbial Richness and Alters Microbial Functions in an Australian Peatland

Peatland ecosystems cover only 3% of the world’s land area; however, they store one-third of the global soil carbon (C). Microbial communities are the main drivers of C decomposition in peatlands, yet we have limited knowledge of their structure and function. While the microbial communities in the Northern Hemisphere peatlands are well documented, we have limited understanding of microbial community composition and function in the Southern Hemisphere peatlands, especially in Australia. We investigated the vertical stratification of prokaryote and fungal communities from Wellington Plains peatland in the Australian Alps. Within the peatland complex, bog peat was sampled from the intact peatland and dried peat from the degraded peatland along a vertical soil depth gradient (i.e., acrotelm, mesotelm, and catotelm). We analyzed the prokaryote and fungal community structure, predicted functional profiles of prokaryotes using PICRUSt, and assigned soil fungal guilds using FUNGuild. We found that the structure and function of prokaryotes were vertically stratified in the intact bog. Soil carbon, manganese, nitrogen, lead, and sodium content best explained the prokaryote composition. Prokaryote richness was significantly higher in the intact bog acrotelm compared to degraded bog acrotelm. Fungal composition remained similar across the soil depth gradient; however, there was a considerable increase in saprotroph abundance and decrease in endophyte abundance along the vertical soil depth gradient. The abundance of saprotrophs and plant pathogens was two-fold higher in the degraded bog acrotelm. Soil manganese and nitrogen content, electrical conductivity, and water table level (cm) best explained the fungal composition. Our results demonstrate that both fungal and prokaryote communities are shaped by soil abiotic factors and that peatland degradation reduces microbial richness and alters microbial functions. Thus, current and future changes to the environmental conditions in these peatlands may lead to altered microbial community structures and associated functions which may have implications for broader ecosystem function changes in peatlands.

Characterization of phosphorus sorption and microbial community in lake sediments during overwinter and recruitment periods of cyanobacteria.

The release of endogenous phosphorus from lacustrine sediment is a key element of freshwater eutrophication. The microbes in sediments may affect phosphorus migration and transformation during the growth of cyanobacteria, which may lead to the release of phosphorus from sediments and contribute to water eutrophication. To study phosphorus sorption and the microbial community structure in the overlying water and the vertical depth of sediments, samples in Meiliang Bay were collected during the dormancy and resuscitation phases of cyanobacteria. The results showed that there were high total phosphorus (TP) concentrations in the overlying water and sediment, with maximum values reached 0.24 mg L−1 and 1059 mg kg−1, respectively. Fitting by modified Langmuir model indicated that the partitioning coefficients (KP) was, from greatest to least: bottom sediment (maximum of 0.923 L g−1) > middle sediment (0.571 L g−1) > surface sediment (0.262 L g−1). During the cyanobacteria resuscitation stage, the relative abundance of Proteobacteria (18.37%–33.56%), Chloroflexi (9.57%–17.76%), Cyanobacteria (0.38%–2.62%), and the Nitrospirota phylum Thermodesulfovibrionia (4.61%–10.14%) were higher than the dormant period of cyanobacteria, and bacteria with phosphorus-solubilizing (27.27%–52.01%) accounted for the majority. The redundancy analysis (RDA) found that the structure of the microbial communities in sediments was significant correlation with organic phosphorus (OP) (P = 0.002) during recruitment period of cyanobacteria, which would accelerate the conversion of OP into soluble inorganic phosphorus and then gets released from sediment to water. The most predominant phylum among phosphorus-solubilizing bacteria (PSB) is Proteobacteria, followed by Actinobacteriota, which were positively correlated with equilibrium phosphorus concentration (EPC0) (P < 0.05) during the cyanobacterial resuscitation phase. The sediments from the cyanobacteria resuscitation phase had phosphorus release risk and highlighted the significant role of the bacterial community.

Numerical investigation on light non–aqueous phase liquid flow in the vadose zone considering porosity effects on soil hydraulic properties

AbstractIn the management of light non–aqueous phase liquid (LNAPL)‐contaminated ground, numerical simulation is widely used to analyze LNAPL flow in the unsaturated soil (vadose) zone. Porosity effects on the hydraulic properties of unsaturated soils are highly simplified in existing mathematical models. Some important features, such as the nonlinear relation between porosity and permeability/displacement pressure, cannot be well captured. To address this problem, a new mathematical model was developed in this study, considering porosity effects on hydraulic properties of soils, including the retention behavior and permeability function of LNAPL and water. The newly developed model was implemented in MATLAB using the finite difference method and then verified by the results of a centrifuge test. Then, parametric studies were conducted to investigate the flow of LNAPL upon an active leakage at the ground surface. Based on the computed results, the influence of several factors, such as porosity magnitude, porosity distribution, and soil layering, was revealed. In particular, an increase in the porosity leads to a significant increase in the volume of LNAPL leaked into the ground, the vertical front depth, and the area of contaminated ground. This is mainly because the porosity affects not only the intrinsic permeability but also the relative permeability because (a) the intrinsic permeability of soils is larger at a higher porosity (b) when the porosity is higher, the equilibrium water saturation at a given capillary pressure is smaller. Consequently, LNAPL can achieve a larger degree of saturation and higher relative permeability.

Seismic reflectivity, fracturing and stress field data from the FFC-1 exploratory geothermal project in SW Skåne, Sweden

Enhanced geothermal systems (EGS) are a potential heat source in many parts of the world, even in locations where the temperature gradient is relatively low. We present here an integrated study of reflection seismic data, borehole logs and seismicity analysis performed in conjunction with a geothermal exploratory project operated by E.ON in Malmö, Sweden. In 2020, the pre-existing 2.1 km deep FFC-1 borehole through the sedimentary cover was deepened into the crystalline basement to about 3.1 km vertical depth. Combined interpretation of the reflection seismic data and geophysical wireline logs show that most of the reflectivity in the Precambrian basement is likely generated by lenses of mafic amphibolite embedded in a felsic gneissic matrix. The general structural bedding and foliation is gently dipping to sub-horizontal, similar to other locations in southwest Sweden. Fracture frequency is relatively high in the crystalline rock mass, with heavy fracturing in the uppermost part of the crystalline basement, obscuring a clear reflection from the top of the Precambrian. Highly fractured and hydraulically conductive intervals are also found between 2,562 and 2,695 m based on a temperature drop and the interpretation of the geophysical data. Open fractures, both natural and induced, have a clear N–S orientation, contrasting with the expected NW–SE direction based on the orientation of the Sorgenfrei-Tornquist Zone and earthquake fault plane solutions to the north. This difference may be partly explained by local variations in the stress field near the FFC-1 borehole and vairations in the stress field with depth. Despite this, the data from the FFC-1 well provide novel and unique information on the complex physical state of the crystalline basement on the margin of the Fennoscandian Shield, which further addresses the need for obtaining in-situ stress data to fully understand the local stress field prior to any stimulation. A temperature of 84°C measured at 3 km depth indicates that a desired EGS temperature of 120–140°C may be reached at 5–6 km depth, assuming a temperature gradient of about 20°C. If the relatively high fracture frequency and occurrence of fracture zones down to 3.1 km are also present at these target depths, then the FFC-1 location may be suitable for heat extraction if the rock mass is properly characterized before stimulation.

Cadmium Enrichment and Bioavailability of Quaternary Profiles in Nansha District, Guangzhou, China

Comprehending the distribution pattern and enrichment rule of the heavy metal cadmium (Cd) in soil and grasping its activity and influencing factors is crucial for guaranteeing the soil environment safety of agricultural and construction land and improving the overall quality of the soil environment. The concentration of heavy metal Cd in the quaternary profile of Nansha was measured, and the pollution level was evaluated using the geographical accumulation index (Igeo) and potential ecological risk index (Er). Then, we determined the correlation between the total amount of Cd and the physicochemical properties of the soil using factor analysis (FA-MLR). The results showed that the average content of Cd in shallow soil (0-20 cm) in the Nansha area was 0.54 mg·kg-1, and the soil was mainly weakly acidic and neutral. The average content of Cd in deep soil (150-200 cm) was 0.42 mg·kg-1, and the soil was mainly neutral. At the same time, the variation coefficient of Cd content in shallow soil was significantly greater than that in deep soil, and Cd content tended to be consistent with the increase in depth. The Cd content of quaternary sediments showed a bimodal distribution with depth, reaching a peak at 20-25 m and 5-10 m, respectively, whereas the core sediments in this section were mostly marine sediments of silt and silty clay, with high cation exchange capacity and organic matter. The Igeo and Er of Cd in the fine-grained sediments dominated by clayey soil were significantly higher than those in the coarse-grained sediments dominated by sandy soil. The difference in soil pH value led to the different trend of Cd content with depth; the migration amount and vertical migration depth of Cd in deep soil were greater in the acidic environment. The influence of pH change on the migration and transformation of Cd was not completely reflected in the influence on the total amount of Cd, but more importantly, it changed the effective state of Cd, thus affecting the bioavailability of Cd. The unstable Cd composed of water-soluble, ion-exchangeable, and carbonate states accounted for 37.92%-49.10% of the total Cd, resulting in a strong instability of soil Cd. Further investigation on the migration and toxicity of heavy metals associated with human health risks is needed in future studies.

Techno-economic approach for optimum solar assisted ground source heat pump integration in buildings

Two-step approach for optimum solar assisted ground source heat pump integration in buildings is proposed. At the first step energy targeting based on dynamic pinch analysis allows to target the energy and optimum equipment size according to buildings’ dynamic demands, and as a result, several energy efficient daily design candidates are extracted. At the second step of the proposed approach, a final design working for the whole year is selected among all the candidates by computing the total annual cost (TAC). A special algorithm is proposed to compute the yearly average energy and capital cost penalty for complementary hot/cold utilities in order to adapt the daily designs to the overall year design. As an objective function, TAC is defined for a 20-year lifetime design. Moreover, the TAC of several daily optimum designs (DOD) based on different scenarios are investigated for a multifamily test building. In the context of Canadian market, it is illustrated that the choice of the overall year integration design depends mainly on the electricity cost. For example, with Quebec electricity cost (i.e., 0.073 CAD/kWh), the DOD of September is optimal for the whole year, where there is no need for vertical ground heat exchangers. However, if Canadian average electricity cost (i.e., 0.147 CAD/kWh) is considered, the DOD of March is optimal for the whole year, with a vertical ground heat exchanger depth of 200 m. The DOD of September and March can reduce building’s annual electricity consumption by 55.9% and 79.2%, respectively.

Target-Hitting Probability Prediction of Landing Point for a Horizontal Well

Summary The uncertainties of the reservoir depth and wellbore position derived from the measurement error of the well trajectory means that entering the landing point of a horizontal well is challenging. In many cases for horizontal well trajectory control, the influence of depth error on the target probability is not considered because methods of analyzing the effects of position uncertainty quantitatively are lacking. This study considers the effects of uncertainty of the wellbore position and that of the vertical depth of the reservoir on the horizontal well in terms of hitting a target. We assume that the wellbore position and target depth conform to the law of normal distribution. Accordingly, a horizontal well target-hitting probability prediction model is established. With the four aspects of random, system, well-by-well and global errors considered, 14 error sources and error weight functions that affect the measurement depth are first determined. The error theory is then used to establish a calculation model for the error of measurement depth as well as a method for predicting the probability of hitting the landing point in a horizontal well. This method not only can be used to predict the target-hitting probability of the landing point, but it can also be used to analyze various factors that affect the target entry in the horizontal well. This research also provides a theoretical basis for selecting marker beds and conducting well trajectory design to effectively improve the target-hitting probability in horizontal wells.

Impact of Assimilating Adaptively Thinned AIRS Cloud-Cleared Radiances on the Analysis of Polar Lows and Mediterranean Sea Tropical-Like Cyclone in a Global Modeling and Data Assimilation Framework

Abstract Polar lows, and mesoscale convective cyclones bearing resemblance to tropical cyclones but originating outside of the tropics, are storms that are challenging to represent accurately in global analyses and models because of their small size, rapid growth at subsynoptic scales, occurrence in data poor oceanic regions, and difficulties in objectively validating them in analysis. Building on previous positive results obtained with respect to the representation of tropical cyclones (TCs) in a global model, a set of observing system experiments (OSEs) performed using the NASA Goddard Earth Observing System (GEOS, version 5) are investigated, focusing on three case studies—a polar low in the Sea of Okhotsk, a polar low in the Southern Ocean, and a Mediterranean Sea tropical-like cyclone that occurred during the boreal fall season of 2014. Experiments assimilating adaptively thinned cloud-cleared hyperspectral infrared radiances from the Atmospheric Infrared Sounder (AIRS) instrument on board the NASA Aqua satellite, with higher density in the vicinity of each storm and its pre-cyclogenesis environment, and lower density elsewhere, demonstrate a positive impact on the analyzed representation of each storm. The adaptive thinning experiments improve the storm intensity and structure, including vertical alignment, depth, symmetry, strength, and compactness of warm core compared to the reference experiments. The results suggest that jet-level processes associated with extremely strong horizontal velocity gradients as represented in the model analysis can be useful to locate dynamically active regions of the extratropical atmosphere where denser data coverage is likely to improve the analyzed representation of polar lows and other similar marine mesoscale convective cyclones. Significance Statement Extratropical maritime mesoscale convective cyclones are short-lived, elusive features that are difficult to represent accurately in global analyses. Previous work by this team demonstrated a positive impact of an adaptive thinning methodology for infrared radiances applied to the tropical cyclone (TC) analysis. The methodology allows a relatively greater volume of radiance data to be assimilated around TCs within a TC-centered moving domain in a global model, yielding an improvement in TC structure and intensity forecast. A similar approach is explored here for two polar lows and a Mediterranean Sea tropical-like cyclone, wherein infrared radiances are more densely assimilated in the vicinity of each storm and its pre-cyclogenesis environment, resulting in a positive impact on the representation of the storm. Strong jet-level horizontal velocity gradients appear to precede each storm, and could be used to automate the adaptive thinning strategy in the future.

E&amp;P Notes (July 2022)

E&amp;P Notes (July 2022)

Soil moisture distribution pattern of surface drip irrigated mango

At present, Pakistan has been facing acute shortage of irrigation water and farmers have been using conventional irrigation methods for orchards, such as flood and basin irrigation, thus wasting huge amount of fresh water. Therefore, it is necessary to find efficient irrigation methods to cope with this major burning issue. The micro drip irrigation method is considered efficient but in the case of mango orchards there is a problem of irrigation frequency, number of emitters, and duration of flow from emitters to meet water demand. Considering the above, an experiment was conducted in the experimental field of the Sindh Agriculture University, Tandojam, by installing the drip system with two circular peripheries of lateral lines in clay loam soil covering the entire canopy of a mature mango tree. The radius of the first and second periphery around the tree trunk was 100 cm and 150 cm, respectively. Four emitters with 4 dm3∙h –1 discharge of individual dipper were fixed in each periphery. Emitters were tested for six different irrigation times, i.e. 1, 2, 3, 4, 5 and 6 h, to observe the moisture distribution pattern. Hydraulic characteristics, such as density, field capacity, porosity, infiltration rate, available water and permanent wilting point (PWP), were determined using standard methods (1.4 g∙cm –3, 33%, 49%, 8 mm∙h –1, 12.41% and 20% respectively). The texture class of the soil profile was determined as clay loam at the soil depth 0–120 cm. Fifty soil samples were collected at 0–10, 10– 30, 30–60, 60–90, and 90–120 cm depths and at 0–20, 20–40, 40–60, 60–80 and 80–100 cm distances on two opposite sides of emitters. The emitters provided sufficient moisture up to field capacity in clay loam soil with flow duration of 4 h. The maximum moisture distribution efficiency was 77.89% with flow duration of 4 h at vertical depth of 0–120 cm and 0–100 cm distance horizontally among four emitters as compared to 1, 2, 3 h flow duration which under irrigated the canopy area and 5, 6 h flow duration which excessively irrigated the canopy area of the mango tree. The water demand of the mango tree was met by 4 h flow duration which provided adequate moisture to the entire canopy up to 120 cm depth in the root zone and water saving was calculated as 15.91% under the installed drip irrigation system as compared with the conventional (basin) irrigation method.

Contrasting Responses of Multispatial Soil Fungal Communities of Thuja sutchuenensis Franch., an Extremely Endangered Conifer in Southwestern China.

ABSTRACTThuja sutchuenensis Franch. is an endangered species in southwest China, distributed sporadically in mountainous areas. Soil property and soil fungal community play a crucial role in plant growth and survival. Nevertheless, understanding soil properties and the soil fungal community in the areas where T. sutchuenensis is distributed is extremely limited. Hence, this study collected a total of 180 soil samples from five altitudinal distribution areas (altitudinal gradients) and three vertical depths throughout four horizontal distances from the base of each tree. The results found that altitudinal gradients and vertical depths altered soil properties, including pH, organic matter content, water content, total nitrogen, phosphorus, and potassium, and available nitrogen, phosphorus, and potassium. The fungal alpha diversity indexes (Chao1 and Shannon) and beta diversity were dramatically decreased with elevation. In addition, high altitudes (2,119 m) harbored the highest relative abundance of ectomycorrhizal fungi (27.57%) and the lowest relative abundance of plant-pathogenic fungi (1.81%). Meanwhile, we identified a series of fungal communities, such as Tomentella, Piloderma, Cortinarius, Sebacina, and Boletaceae, that play an essential role in the survival of T. sutchuenensis. The correlation analysis and random forest model identified that water content and total phosphorus showed strong relationships with fungal characteristics and were the primary variables for Zygomycota and Rozellomycota. Collectively, the findings of this integrated analysis provide profound insights into understanding the contrasting responses of T. sutchuenensis soil fungal communities and provide a theoretical basis for T. sutchuenensis habitat restoration and species conservation from multispatial perspectives.IMPORTANCE The present study highlights the importance of fungal communities in an endangered plant, T. sutchuenensis. Comparative analysis of soil samples in nearly all extant T. sutchuenensis populations identified that soil properties, especially soil nutrients, might play critical roles in the survival of T. sutchuenensis. Our findings prove that a series of fungal communities (e.g., Tomentella, Piloderma, and Cortinarius) could be key indicators for T. sutchuenensis survival. In addition, this is the first time that large-scale soil property and fungal community investigations have been carried out in southwest China, offering important values for exploring the distribution pattern of regional soil microorganisms. Collectively, our findings display a holistic picture of soil microbiome and environmental factors associated with T. sutchuenensis.

New formulation of the two-dimensional steep-slope shallow water equations. Part I: Theory and analysis

Two-dimensional (2D) depth-averaged shallow water equations (SWE) are widely used to model unsteady free surface flows, such as flooding processes, including those due to dam-break or levee breach. However, the basic hypothesis of small bottom slopes may be far from satisfied in certain practical circumstances, both locally at geometric singularities and even in wide portions of the floodable area, such as in mountain regions. In these cases, the classic 2D SWE might provide inaccurate results, and the steep-slope shallow water equations (SSSWE), in which the restriction of small bottom slopes is relaxed, are a valid alternative modeling option. However, different 2D formulations of this set of equations can be found in the geophysical flow literature, in both global horizontally-oriented and local bottom-oriented coordinate systems. In this paper, a new SSSWE model is presented in which water depth is defined along the vertical direction and flow velocity is assumed parallel to the bottom surface. This choice of the dependent variables combines the advantages of considering the flow velocity parallel to the bottom, as can be expected in gradually varied shallow flow, and handling vertical water depths consistent with elevation data, usually available as digital terrain models. The pressure distribution is assumed linear along the vertical direction and flow curvature effects are neglected. A new formulation of the 2D depth-averaged SSSWE is derived, in which the two dynamic equations represent momentum balances along two spatial directions parallel to the bottom, whose horizontal projections are parallel to two fixed orthogonal coordinate directions. The analysis of the mathematical properties of the new SSSWE equations shows that they are strictly hyperbolic for wet bed conditions and reduce to the conventional 2D SWE when bottom slopes are small. Finally, it is shown that the SSSWE predict a slower flow compared with the conventional SWE in the theoretical case of a 1D dam-break on a frictionless channel with fixed slope. The capabilities of the proposed model are demonstrated in a companion paper on the basis of numerical and experimental tests.

Concurrent 1. Presentation for: Reservoir quality and diagenesis of the West Erregulla field, North Perth Basin, Western Australia

Presented on Tuesday 17 May: Session 1 The West Erregulla field is the deepest onshore gas discovery in Australia today, with three wells drilled to more than 5000 m vertical depth. The reservoir quality has been preserved at depth by clay coating, which shows a similar trend with core from other shallower fields in the northern Perth Basin such as Waitsia and Beharra Springs Deep. The primary reservoir in the West Erregulla field is the Permian Kingia Sandstone that was deposited in a tidal estuary environment, which allowed for mixing of meteoric and saline waters. This depositional setting has been inferred from core, image logs and seismic interpretation. This setting resulted in quartz grains coated in chlorite/illite that has limited quartz overgrowth cements and maintained intergranular porosity. This paper presents Strike’s interpretations of the depositional environment that resulted in the anomalous depth–porosity trend based on core analysis, high-resolution borehole image log interpretation and cuttings. To access the presentation click the link on the right. To read the full paper click here

Concurrent 5. Presentation for: Seamless in seam – new geosteering technology delivered challenging coal seam gas project with success

Presented on Tuesday 17 May: Session 5 A recent coal seam gas (CSG) appraisal project posed several challenges. The target reserve area had limited seismic data available and yet had complex structure with several faults of variable orientations and throws between 2 and 25 m. Dual-lateral extended-reach drilling (ERD) wells needed to be drilled in order to access this reserve, with a 1000 m in-seam section for each lateral planned to maximise production. Conventional technologies for CSG projects included motor bottom hole assembly with a boundary mapping tool for geosteering in the coal seams. However, for drilling ERD wells in this unknown area, these methods were insufficient to deliver success, due to the limited mapping capabilities and drilling efficiencies. Recently there has been significant development on the directional resistivity-based mapping tool, on both the measurements and processing. The operator adopted a new mapping-while-drilling technology which has the first-in-industry tool with axial, tilted and transverse antennas integrated in one module. This new technology can provide high-resolution multilayer mapping with doubled depth of investigation, even when drilling out of the coal seam. The results from utilising this new tool, together with a rotary steerable system for directional control, were very encouraging. The new multilayer mapping-while-drilling tool mapped both the top and base of the coal seam throughout horizontal sections in-seam. In addition, it detected the coal seams during landing and after fault-crossing from up to 4 m true vertical depth away, enabling the team to navigate through complex fault zones confidently, and to deliver the project with success. To access the presentation click the link on the right. To read the full paper click here

Analysis of drilling difficulty of extended-reach wells based on drilling limit theory

With the continuous increase in vertical depths and horizontal displacements of directional wells, the difficulties of drilling operations continue to increase, and more accurate methods of drilling difficulty evaluation are needed. In this paper, a drilling difficulty evaluation method is built by combining drilling limit model and expert evaluation. Firstly, the concept of drilling difficulty index is introduced, and the method to calculate drilling difficulty index is established. Next, the meanings of five drilling difficulty levels are explained and the optimization design method with drilling difficulty as the target is built. At last, the theoretical model is applied to the extended-reach drilling of the Liuhua oilfield in the South China Sea, in which drilling difficulties are evaluated and the relationship between drilling difficulty and development control radius is revealed. The results indicate that extended-reach drilling in the Liuhua oilfield is on the “normal” difficulty level on average, rotary drilling in 8 1 / 2 -in. section is the most difficult, and the main constraint conditions are excessive torque and high friction. Through technology upgradation, the drilling difficulties are decreased, the development control radius increases from 6.6 to 11.4 km, and the maximum horizontal-to-vertical ratio increases from 5.3 to 8.7. Then, the development wells in marginal oilfields and adjustment wells in old oilfields can be drilled on “normal” difficulty level. Therefore, technology upgradation, especially drilling rig upgradation, is the most important development direction for extended-reach drilling in the South China Sea.

Application of Recursive Estimation to Heat Tracing for Groundwater/Surface‐Water Exchange

We present and demonstrate a recursive‐estimation framework to infer groundwater/surface‐water exchange based on temperature time series collected at different vertical depths below the sediment/water interface. We formulate the heat‐transport problem as a state‐space model (SSM), in which the spatial derivatives in the convection/conduction equation are approximated using finite differences. The SSM is calibrated to estimate time‐varying specific discharge using the Extended Kalman Filter (EKF) and Extended Rauch‐Tung‐Striebel Smoother (ERTSS). Whereas the EKF is suited to real‐time (“online”) applications and uses only the past and current measurements for estimation (filtering), the ERTSS is intended for near‐real time or batch‐processing (“offline”) applications and uses a window of data for batch estimation (smoothing). The two algorithms are demonstrated with synthetic and field‐experimental data and are shown to be efficient and rapid for the estimation of time‐varying flux over seasonal periods; further, the recursive approaches are effective in the presence of rapidly changing flux and (or) nonperiodic thermal boundary conditions, both of which are problematic for existing approaches to heat tracing of time‐varying groundwater/surface‐water exchange.

Clinical and Radiographic Evaluation of Applying Atorvastatin 1.2% Bio Adhesive with Plasma Rich in Growth Factor (PRGF) for Treatment of Mandibular Class II Furcation Defects: a Randomized Clinical Trial.

Statement of the Problem: Molar teeth with furcation involvement are one of the most common problems in patients with periodontal disease. Regeneration methods are of the most controversial treatment strategies for these lesions.Purpose: The purpose of this study was to determine the effect of plasma rich in growth factors (PRGF) with 1.2% Atorvastatin (ATV) in the treatment of furcation involvement of mandibular molars.Materials and Method: The present randomized clinical trial was conducted on 15 patients with moderate periodontitis and class II furcation involvements; 24 defects were located in four groups of six, including debridement, ATV1.2%, PRGF, PRGF with ATV1.2%. The parameters of vertical probing depth (VPD), vertical clinical attachment level (VCAL), gingival index (GI), horizontal probing depth (HPD) and gingival recession (GR) were measured at baseline (T0), immediately before surgery (T1), 3 (T2), and 6 (T3) months after surgery. Moreover, the bone conditions were evaluated by digital subtraction radiography before and six months after surgery. Data were analyzed using SPSS23 software.Results: No significant difference in radiographic parameters was observed among the groups (p= 0.08). There was no significant difference in the mean levels of VPD, VCAL and HPD among the groups at different times (p<0.05). Comparison of clinical parameters of VPD, VCAL and GI in the treatment groups compared to the baseline showed a significant improvement in each group (p< 0.05) but there was no significant difference among different groups (p< 0.05).Conclusion: The use of PRGF with ATV 1.2% in grade II furcation involvement in mandi-bular molars was effective in the improvement of clinical and radiographic parameters six months after treatment, but this effect revealed no difference in comparison with the other groups.

Coiled Tubing Program Succeeds in Harsh-Environment Tight Gas Wells

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 209032, “Successfully Adapting and Overcoming Challenges for Coiled Tubing Applications in High-Pressure Sour Environments and Horizontal Unconventional Tight Gas Wells in UAE,” by Ole Sorensen, Yang Wu, and Didier Caillon, SPE, TotalEnergies, et al. The paper has not been peer reviewed. During the completion phase of four unconventional wells in the United Arab Emirates, a detailed engineering approach overcame challenges presented by extreme conditions of pressure, temperature, and a sour environment across long horizontal sections to carry out cleanout activities successfully. This operation, the first of its kind in the country for the operator, yielded lessons for design considerations and the execution process and recommendations for coiled tubing (CT) intervention in similar working environments. It also confirmed that 110,000-psi-yield-strength quench-and-tempered (Q&amp;T) CT strings can be deployed safely in a high-pressure sour environment by implementing proper risk-mitigation strategies. Introduction The unconventional gas play (referred to as “A” in the complete paper) featured a reservoir pressure of nearly 13,000 psi and a bottomhole temperature of approximately 325°F. The environment was sour, with 5 mol% of hydrogen sulfide (H2S) and 5% carbon dioxide (CO2). The well’s architecture consisted of a 5½-in. monobore completion with cemented casing and horizontal sections ranging from 5,000 to 8,200 ft. The selected completion methodology was plug-and-perf, including up to 35 fracturing stages in a single well. Overview of CT Intervention Challenges The true vertical depth of the play was 12,600 ft on average, representing a maximum anticipated surface pressure (MASP) of 8,000 psi with the wellbore full of working fluid (8.34-lbm/gal slickwater) and a maximum potential wellhead pressure (MPWHP) of 11,300 psi with the wellbore full of gas. Also, partial pressures of H2S and CO2 exceeded 600 psi at bottomhole conditions, confirming that sour- and corrosive-service programs had to be implemented fully in this project. Convergence of MASP above 7,500 psi, CT dynamic pressure of greater than 11,000 psi, lateral length of up to 8,200 ft, and the sour and corrosive environment required a highly engineered approach on the design and selection of the CT string and configuration of the surface equipment.

New String Deployment Concept Extends Operational Limits for Megareach Interventions

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 22577, “Extending the Operational Limits To Target Megareach Interventions With Coiled Tubing: A Study of the First 40,000-ft-Long CT String Deployment Using Uniquely Engineered Energy Transportation Solutions,” by Karan Kaul, Nicolas Dupouy, and Jose Jimenez, Halliburton, et al. The paper has not been peer reviewed. Copyright 2022 International Petroleum Technology Conference. Reproduced by permission. An operator requiring an offshore coiled tubing (CT) intervention into 40,000-ft-deep wells from artificial islands of the United Arab Emirates encountered challenging crane and transportation limitations to lift a 2⅜-in. CT reel weighing approximately 200,000 lbm. This, combined with a desire to improve operational efficiency in moving from well to well and eliminating large mechanical lifts, led to the design of a custom-engineered transportation solution for the large-diameter, heavy CT spool. Introduction CT and its associated setups are in high demand for wellbore intervention to perform operations such as valve or sleeve shifting, pinpoint stimulation with custom chemistry, milling, fishing, wellbore diagnostics using fiber optics, and drilling with different downhole tools. These tasks become even more challenging when difficulties associated with extended-reach maximum-reservoir-contact reservoirs are considered. While the term “extended-reach” refers to wells for which the measured depth (MD) is greater than twice the true vertical depth (TVD), the term “megareach” refers to wells for which the MD is greater than three times the TVD. A CT string is a continuous string of pipe manufactured from a specific grade of material determined by the downhole application for which it is intended. It is coiled over a drum (referred to in the paper as a spool) with more than 25 full layers around the bed wrap and has a high amount of energy stored in it because of the residual bending of the CT material. Although the string is secured at the end with an industry-specific clamp, close monitoring is required to avoid loosening from vibrations caused during transportation. After storing the CT pipe on the spool, the spool usually is shipped and transported from the shore jetty to the artificial island jetty using a conventional vessel. It is then offloaded, lifted, and secured onto a CT drive reel using a regular crane ready for wellsite operations (Fig. 1).