An operator is drilling exploration wells near Xanab field in Mexico's Southwest Marine region. The 8½-in. hole section is difficult to drill, with damaging shocks and vibrations occurring in the hard/interbedded Cretaceous carbonates. These formations, with relatively high unconfined compressive strength (UCS) of 15,000 to 28,000 psi combined with alternating lithologies with chert nodules, have been drilled mostly with roller cone IADC-527X bits. Although the roller cone produced vibration-free operations, suboptimal rates of penetration (ROP) and short run lengths resulted in multiple trips to total depth (TD) of the section. Attempts were made to design polycrystalline diamond compact bits (PDCs) that could endure the difficult downhole environment by increasing diamond volume per blade. However, when encountering the hard formations, high vibration levels were still causing broken cutters in the nose/shoulder areas.
In a new exploration well, a new fixed cutter bit was used. The bit is equipped with stinger conical diamond elements (CDE) with an ultrathick diamond layer that improves impact resistance, along with PDC cutters. A modeling system based on finite-element analysis (FEA) was used to design a new-type eight-bladed hybrid bit by positioning CDEs and PDCs from bit center to gauge on all eight blades. The unique cutter pattern would fail the rock with a combination of plowing and shearing action. To ensure all CDEs engage the formation at the beginning of the run, the elements were positioned at a height equal to the top edge of the conventional PDC cutters. This strengthens the bit by leveraging the superior impact strength of the CDEs. To deliver sufficient torque and to keep a vertical trajectory, a rotary steerable system (RSS) was selected, with an integrated positive displacement motor (PDM) to supply additional power.
The bottomhole assembly (BHA) was run on the Keluk-1 well and drilled to TD in two runs, 30% faster (2.59 m/hr) than the average ROP of the nine 8½-in bit runs (seven with PDC and two with roller cone bits) in Xanab field (2.0 m/hr). The first bit run made 206 m and could have finished the entire section but was pulled for downhole tool failure. The second bit drilled 65 m to TD. This compares favorably to the nine-well offset average of 176 m. The RSS/motor combination worked as planned, providing the CDE bit with the necessary energy to maximize ROP while reducing stick/slip occurrence to less than 20% during the run. The reduced vibrations enabled the operator to maintain RPM (150 to 170) and weight on bit (WOB) (10 to 16 ton) when drilling the critical middle/lower Cretaceous mudstone with chert nodules. Previous runs in this section required reduced parameters to mitigate vibration, thus slowing ROP.
Both bits were pulled out in excellent dull condition (0-1/0-0) verifying that the CDEs provided the added durability needed to drill through the challenging application. The increase in drilling performance saved 90 hours of rig time equaling USD 320,000. Field testing of other CDE bits are producing favorable performance results combined with larger drill cuttings for improved formation evaluation.
According to our country needs and limitations to oil reserves access and since some productive areas are boundary to protected zones and moreover, Andes Petroleum Ecuador Ltd. concern about environmental impact to those natural reserves, the Company developed a plan to drill the longest displacement well in Ecuador (ERW).
SEED is an expression of the spirit of integral and ethical service that the oilfield services company has with its clients and community. The SEED (Schlumberger Excellence in Educational Development) program focuses on education and inclusion for the common good, especially in the vulnerable sectors of society, such as children, youth and people with special needs, and Down syndrome and mental disabilities. Ecuadorian legislation requires that 4% of company staff be people with special needs; nevertheless, the oilfield services company goes further than hiring people from this vulnerable sector. We create true inclusion of people with mental disabilities and Down syndrome in the work, social, educational and professional environment. The Company works with 6 institutions that accept people with various disabilities, and focuses on various aspects of inclusion in education with 3 special education schools in the amazon region. It has provided these schools with technology and training for teachers in technological areas, and how to create projects that focus on solutions for students with special needs and improving teaching for their day-to-day learning. In the case of the Special Needs School, "3 de Diciembre" in Lago Agrio, it has provided them with a physical rehabilitation room with equipment such as: stationary bicycles, electro-stimulation equipment, physical therapy and hydro massage, etc. Regarding inclusion in the work area, along with Fundación General Ecuatoriana and the Vice President's Office of the Republic of Ecuador, and Fundación El Triángulo, we currently have 26 youth with mental disabilities and Down syndrome on our local payroll, and 7 of them work directly in the main offices with the same guarantees and benefits as all of our workers. Regarding sports inclusion, we work with the "School of wheelchair tennis" in Quito. This school provides a space for people with physical, mental and visual disabilities to practice sports.
This paper provides a method to estimate pressure drops due to skin damage using information from production logs (PLTs).
The analysis of the temperature measurements and flowing rates, enable calculating flowing temperatures of each layer and its differences with the natural geothermal profile.
The behavior of pressure and temperature are related according to thermodynamic functions (changes of pressures imply changes of temperatures).
Gas expansion due to formation damage or skin, occurs within a short distance of the wellbore. Due to small transient times and transfer areas, there will be no enough heat conduction from below (or above) to stabilize the gas temperature back to its corresponding natural temperature gradient.
Conversely, pressure drops due to Darcy flowing mechanism, distribute in larger zones, (especially in low permeability or fractured wells), allowing in this case significant heat conduction to reduce the associated temperature changes.
Most of the temperature changes can be allocated to the skin effect, where no significant heat transfer occurs (adiabatic) and the process can be considered isenthalpic. In this condition, the pressure drop of the gas flowing through a damaged zone can be derived from the Joule-Thomson coefficient and the temperature changes.
More than 150 PLT logs were analyzed with this method. Having compared results from all cases, particular candidates were selected for stimulation or re-perforating. The results from interventions on the selected wells were positive in strong agreement with the conclusions of this paper.
This paper shows the results of the Lower U Sandstone prediction of Limoncocha Oilfield using the pre-stack elastic seismic inversion method, based on available well and seismic data. This study was focused to reduce the uncertainty in the location of new wells. The Poisson's Ratio (PR) is the most sensitive elastic parameter for discriminating lithology. Data of 49 wells were used in this study and the cross-plots analysis between mean PR obtained of seismic inversion and sand net thickness gotten of the wells show the best correlation (90%). Based on the results of this study 21 new wells were located and drilled, including horizontal and sidetrack wells. Currently, the cross-plots between these parameters in the Lower U Sandstone, including the new wells, keep a high correlation (83%). These results show the validity of this method for predicting the net sand thickness of the Lower U reservoir in the Limoncocha Oilfield. Production data were also correlated with the mean PR, and the best production matches with thickest sand development. Maybe this method could be applied in other Oilfields with similar results.
With the depletion of current oil reserves, drilling engineering is emerging to even more challenging environments. The pre-salt carbonate reservoirs is an example of that, now at the pinnacle of the Brazilian development projects, these reservoirs are located around 200km away from coast, in over 2100m water depth and up to 7000m below sealevel. Since the discovery of these huge fields in 2007 it was believed that the biggest challenge is to overcome the thick salt layer but nowadays drilling into the reservoir has become even more challenging. Carbonate formations are very heterogeneous and total losses are often experienced when fractures or vugs are encountered. The lost circulation in high rates can result in a well control issue if gas starts to flow into wellbore, manly it occurs due to loss of hydrostatic pressure. Pressurized Mud Cap Drilling (PMCD) is one of Managed Pressure Drilling (MPD) variations applied in situations where total or severe losses are experienced. This paper addresses a discussion regarding the application, fluid selection, safety consideration and well control issues using this technique.
This paper discusses a different approach to defining rock types and lithofacies performed for the Hollin formation located in the Palo Azul field of Ecuador. The study includes a spectrum of depositional environments, which significantly influences geometry, diagenesis, and quality of the Hollin reservoir. This work integrates lithofacies and petrophysical properties using well log data, core, and sedimentological analyses to define rock types.
Sedimentological analyses were performed to describe existing cores, thin sections, and X-ray diffraction results. Flow units were identified using flow zone indicator (FZI) and reservoir quality index (RQI) methods. These units were classified as functions of flow capacity (K/Phi) based on capillary pressure (Pc) and other special lab analyses. Capillary pressure enabled the grouping of rock flow units in accordance with the K/Phi ratio, similar RQI, and irreducible water saturation (Swirr) values. These rock types (RT) were correlated with the lithofacies identified using sedimentological analysis.
The transgressive Hollin formation sequence includes fluvial mid-grained sandstones with cross stratification, tidal mid- to fine-grained sandstones with mud drapes and organic matter, and marine glauconitic sandstones with/without calcareous cement. Integrated sedimentological and petrophysical analysis defined five rock types (RT1-RT5). RT1 and RT2 correspond to tidal quarztarenites and fluvial sandstones with few discontinuous clay laminae, high permeability, and high porosity values. RT3 includes tidal fine-grained sandstones with abundant clay and organic matter in the matrix, which decreases flow capacity. RT4 is characterized by very fine- to fine-cemented tidal sandstones in which the diagenetic events close the porosity and permeability. RT5 is a muddy sequence of tidal/fluvial environments, marine shales, and well-cemented glauconitic sandstones. These rocks present negligible permeability and low porosity. In conclusion, the reservoirs deposited in tidal bars and fluvial channels have major flow capacity and storage characteristics, whereas the rocks of the shallow marine and sand flat environments present poor reservoir quality.
This integrated petrophysical and sedimentological work presents an alternative method for identifying rock types by using flow capacity and the integration of conventional core data, sedimentological analysis, petrographic and diagenetic description, capillary pressure, well logs, and reservoir information. The results from this method were incorporated in the geocellular model for reservoir simulation.
Sierra, F. (Petroamazonas EP) | Teran, N. (Petroamazonas EP) | Bastidas, M. (Petroamazonas EP) | Soria, G. (Petroamazonas EP) | Rojas, E. (Schlumberger) | Villalva, R. (Schlumberger) | Sanchez, J. L. (Schlumberger) | Castro, B. (Schlumberger)
Horizontal well landing in block 7 presents several challenges including reservoir vertical position uncertainty, which is generally anticipated based on seismic models, local formation dip at wellbore position and well path construction following strict directional objectives.
To support landing decisions, a logging-while-drilling (LWD) technology based on deep azimuthal electromagnetic measurements was introduced in the project, not only for conventional well-to-well correlation, but to remotely detect the approaching of the latest geological markers and adjust the trajectory inclination and landing point accordingly. In addition, a real-time gamma-ray borehole image was used to qualitatively identify local formation dip for a more effective planning of the further lateral section. Landing section has also been optimized with the use of a point-the-bit rotary steerable system (RSS), which allowed improved directional control, safer operation and higher build rates, minimizing the need of an additional mud motor run to achieve navigation inclination.
This paper presents case studies of the implementation of well placement and directional technologies to optimize horizontal well landing, and the introduction of a novel deep directional resistivity system to eliminate the need of of drilling a pilot hole.
Bravo, O. (Schlumberger) | Mora, L. (Schlumberger) | Rabanal, J. (Schlumberger) | Vallejo, R. (Schlumberger) | Pastrana, W. (Schlumberger) | Salas, J. (Schlumberger) | Lomas, J. (Petroamazonas EP) | Tapia, D. (Petroamazonas EP) | Almeida, R. (Petroamazonas EP) | Paz, F. (Petroamazonas EP)
The objective of this work is to describe a comprehensive approach integrating static and dynamic data along with rock mechanical properties to optimize well production and avoiding premature sanding problems.
The proposed procedure was used to estimate the production potential of a slanted well in the Napo M1 Sandstone which presents a high sanding potential. Starting with a detailed petrophysical analysis along with advanced sonic scanner data processing, a Mechanical Earth Model (MEM) was built. In addition to the MEM an advanced perforating design and a grain size laboratory test were finally used to develop a Sanding Model Analysis that was used to predict and measure severity of sanding problems under specific static and dynamic conditions.
This holistic approach was used to determine the critical drawdown at which sanding problems could occur. A tailored critical drawdown was determined based on grain size; it was determined that small grains will start moving with drawdown of around 790 psi, while larger grain sizes will move at a drawdown close to 1790 psi. The grain size distribution per sample was then used to determine the level of severity and safe and non-safe drawdown ranges. Finally a safe bottom hole flowing pressure of ~1100 psi or drawdown of ~1190 psi with a 90% safety of no sanding problems was selected as the optimum dynamic condition for producing the well with minimum sanding risk.
The well was put into production using the recommended critical drawdown. No sand production was observed at the surface. After five months of production (from 30-Aug-2014 to 4-Jan-2015), the well had accumulated 9 bbls of sand (equivalent weight: 3650 kg), lower than expected (not showing on surface) and average production was 1126 bbls of fluid per day (1075 bbls of Oil per day, 4.53% water cut), significantly higher than neighbor wells.
This methodology accurately predicted the critical drawdown at which a well with potential sanding problems must be produced. It also provided highly valuable information for a better completions design and decision making on whether to use a sand control equipment or not, representing cost savings and optimizing production.
Budged estimation for a given drilling project is part of the dutties assigned to drilling engineers. The simplest way to make those estimations is using average costs based on previous wells, which works well to a certain degree.
Average time and costs sometimes include troubles experienced in wells that could increase the estimation.
This paper presents a simple procedure to make more realistic estimations based on the actual well design of the wells to be drilled and the information compiled from wells already drilled. The Tapir field in Andespetroleum was used to prove the effectiveness of this approach.
Time estimation for drilling operations is made from the information collected in a database, which considered the previous wells drilled in the Tapir field. Wells were classified by their directional profiles, their displacement, their direction and maximum inclination.
The collected information also included a record of average ROPs for each section of the wells, time spent for each trip, and also the time spent in other operations such as open hole logging, casing running, cementing, wellhead / BOP installation, etc.
Once the conceptual design of the new well is ready, wells with similar profile are searched into the database trying to find one well with the closest possible profile respect to the well being planned. This well is called the pattern well. Then, a simple spreadsheet is used to quickly estimate the time for drilling operations using the pattern well as reference.
Oportunities for time optimization are derived from the lessons learnt from each well.
On the other hand, the cost estimation uses a very simple spreadsheet that collects all the associated services involved in drilling a well. It is important to point out the advantage of having services that are paid using a lump sum (drilling fluids, directional services, cementing, etc) which provides a very simple way to estimate costs with a good degree of accuracy. The lump sum contract model for almost each service was adopted after several years of experience in the area that resulted in a good knowledge of the risks and operations associated.
An example of how to use this simple approach is showed and a comparison for planned versus real time and costs are also presented.