GasPal1. Why did you create GasPal? (Main problem solved?)
GasPal and its predecessors, SRM (1980) & GMAN (1996) were created to provide developers/producers with the engineering information needed to make sound decisions re their gas reservoirs. Briefly the most important decisions are
- What is the economically best number of wells? Payout & rate of return of each?
- What surface flowlines should I install to deliver gas to customers?
- When should I install compressors? And how many?
- What volume rate of gas should I contract to deliver? And for how long?
- How does the capacity rate of each well decline with time?
- How do I schedule production from each well vs time?
- How many BCF of reserves do I have?
The engineering information needed is an accurate prediction of pressure and flow capacity of each well vs time.
Over time users desired to have more details about performance of each individual well. The exponential growth in computing capability made it possible to develop software that responded to this need. Thus, was born GasPal. The core of GasPal is a detailed model of each individual well in a reservoir – number of producing layers, properties of each, details of flow from formation to wellbore, up tubing to wellhead, and through gathering lines into surface pipelines to delivery points.
In parallel with expansion of technical details GasPal’s data handling and results reporting capabilities have mushroomed. Input capabilities and conveniences are continually expanding along with data access and storage. Similarly, convenient output of every aspect of predicted performance in graphs and tables has been extended with an electronic database of results. From the latter comparative graphs showing sensitivity to assumptions, proposed actions and data values can be readily obtained.
2. Who are the intended users?
Users are engineers and planning analysts for gas producers. For example, the largest application is an offshore reservoir with 800+ wells producing through 23 platforms to a pipeline at several MMSCF/D. Wells produce from as many as 30 layers, large and small, distributed vertically over several thousand feet. These are perforated – and plugged – with a variable schedule in each well.
3. Why do they need it?
GasPal fills an essential need. Existing wells are tested and worked over continuously, and newly drilled wells are added to the mix. Without a tool such as GasPal to provide a continually-updated, accurate representation of system performance, efficient operation of a gas producing complex is not in the cards.
4. Why would they want it?
Users want GasPal because it lets them do their job professionally. With GasPal they can make judgments based on sound engineering performance data – and have confidence that their decisions are of professional quality. As we see in the current BP disaster, actions based on incorrect judgments can be horrendously costly.
5. What are GasPal’s features?
- Simulate performance of interconnected, multi-layer, gas reservoirs rapidly
- History match full performance spectrum (Q, P/Z, WGR, CGR, well-tubing-flowline DP)
- Create model, enter data, plot-analyze results, report output via graphic user interface
- Compute fully-implicit nodal analysis (reservoir, tubing and surface network)
- Perforate and plug layers using automated rule-based procedure
- Calculate two-phase (GW) flow in the reservoir with aquifer influx, water drive
- Calculate Darcy/non-Darcy flow (kh, AB, AFBC,C/n, turbulence coeficient), relative permeability curves
- Calculate flow of reservoirs’ gas (plus possibly tariff gas) through surface network of compressors, chokes, loops, splits to multiple off-take points, trace composition and heating value
- Generate production schedules with spare capacity, minimum well ratesBuild complex reservoir grid with GasPal’s pre-processor GRIDDERBuild complex reservoir grid from a PETREL geologic model with GasPal’s UPSCLR
- Tune tubing DP correlations, generate IPR & TI curves using TFR
- Model gas storage reservoirs
6. Who are your competitors?
- Schlumberger — Eclipse
- Fekete (Calgary) FORGAS
- Petroleum Experts (PetEx) in Edinburgh Scotland
7. How does GasPal compare in features?
PetEx’s IPM (Integrated Production Management) holds the lion’s share of the gas market that GasPal is targeted for. Their webpage http://www.petex.com/ifm_products/
claim that their IPM suite “is the only fully integrated reservoir, well, surface network modelling and production optimisation system in the market today” is untrue for gas reservoirs. GasPal’s predecessor, GMAN, has been used by gas operators since 1996 and GasPal since 2003. Both are ‘nodal simulators’ that consider the integrated interaction of gas in the formation, production tubing and surface flow lines when computing flow capacity and cumulative production. IPM consists of three modules, MBAL, PROSPER & GAP. The linkage of these modules to form an integrated model is cumbersome, inefficient and – compared to GasPal – slow.
- MBAL is the reservoir model. It compares to GasPal like a Model A Ford compares to a 2010 Ford Fusion. In MBAL material balance equations are used to compute average pressure in reservoir tanks as gas is produced. GasPal divides the reservoir into interconnected cells – a gridded simulation model. In so doing the material balance for each cell is combined with the well production equation to give an accurate prediction of each well’s performance as gas is produced and cell pressure declines. With an aquifer the calculated rate of advance of the invading water front through out the reservoir grid provides the timing of water break-through into each individual well.
- PROSPER is the well bore flow model. Rather than being integrated with MBAL, it is a separate program to which data is passed. GasPal’s integrated program gives equally accurate predictions of pressure drop in the tubing in a fraction of the time.
- GAP is the surface flow line model. This very detailed, separate program computes performance of surface facilities of surface facilities is also linked only indirectly with MBAL & PROSPER. GasPal’s surface facility calculations are integrated directly with reservoir and tubing calculations so that again speed of obtaining results is much greater. GasPal’s TFR module is a standalone program for calibrating surface facility models with results passed directly to GasPal’s integrated system model.